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Unmanned Spaceflight.com _ MRO 2005 _ Mro On Approach
Posted by: Redstone Feb 3 2006, 11:06 PM
MRO has http://marsprogram.jpl.nasa.gov/mro/gallery/cruise/cruise_approach_200602.html. Apparently, the trajectory is so good that TCM-3 was cancelled. This is good news for the prospects for a long life for MRO supporting future missions. TCM-4 is on Feb 28, and MOI on March 10. Only 5 weeks away! 
Posted by: RNeuhaus Feb 4 2006, 04:41 AM
Good news. I seems that MRO has started to gain its speed due to Mars gravity tug, has not?
What is MOI? Mars Orbit Insertion.
http://mars.jpl.nasa.gov/mro/gallery/cruise/images/cruise_approach_200602.jpg
"It was a very busy time for the team. Many tests were conducted to ensure that the instruments onboard were functioning properly and our navigators performed trajectory correction maneuvers to keep us on a very precise path to Mars."
Speaking of that precision, the third of four possible course corrections was deemed unnecessary this week.
"The navigation solutions have shown a great consistency since the second trajectory correction maneuver was executed on November 18," said Han You, navigation team chief. "More importantly, the current data indicate that the spacecraft aim for insertion into Mars' orbit is well within the projected target. If the current trend continues, the spacecraft will require only a very small nudge to fine tune the final aim."
Rodolfo
Posted by: ugordan Feb 4 2006, 12:13 PM
Where did you hear that? As far as I can see, MRO is sill on the elliptical transfer orbit and too far away to feel Mars' gravity influence. In fact, its heliocentric speed should be decreasing.
MRO won't begin to feel significant pull from Mars probably all the way until around a day or so before MOI.
Posted by: abalone Feb 4 2006, 12:49 PM
I hope they did a double ckeck in metrics and not just rely on the usual NASA units of ancient Kings appendages and Roman marching steps and bushels of wheat, but mistakes like that couldn't happen could they??
Posted by: djellison Feb 4 2006, 03:19 PM
It's odd to think that from 'aboe' - MRO's burn which actually increase it's speed - but because it will being 'run over' by mars, it will be slowing down w.r.t. Mars itself
I hope they release the op-nav imagery - I'm sure it wont be particularly great, but it will make an interesting little movie watchign Phobos and Deimos doing their thing
Doug
Posted by: SFJCody Feb 4 2006, 03:50 PM
How many pixels would HiRise get across the disc of Mars now?
Posted by: mcaplinger Feb 4 2006, 05:26 PM
HiRISE has an IFOV of 1 microradian, so the pixel scale is the distance times 1e-6.
MRO is probably about 7 million km out right now (the simulations on the MRO site don't show the range) so that's 7 km/pixel. Mars is about 7000 km in diameter, so that's about 1000 pixels.
Of course, there are no plans to take such images that I'm aware of. The opnav camera is pointed in a direction almost 180 degrees away from the rest of the science instruments.
Posted by: djellison Feb 4 2006, 05:41 PM
This is from a little PDF I found at the same place as the UHF tracking info
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Posted by: crabbsaline Feb 7 2006, 11:11 AM
Thanks Doug. I had to look up http://mars.jpl.nasa.gov/mro/mission/sc_instru_optical.html to understand that part of the chart. I wonder what kind of "improved navigation capability" that they anticipate it will yield versus older methods?
I hope to see the ONC images soon.
Posted by: djellison Feb 7 2006, 11:57 AM
I think they're using the ONC more as a tech-demonstrator to feed forward to future missions that will require that sort of accuracy. As it is for MRO, 'classical' navigation techniques are probably enough.
They wont be pretty pictures, but they'll be interesting none the less.
Doug
Posted by: jmknapp Feb 15 2006, 01:19 PM
MRO won't begin to feel significant pull from Mars probably all the way until around a day or so before MOI.
True--MRO's speed relative to Mars won't start to increase until Feb. 25, & even then only very slightly until the day of MOI (per the SPICE kernel data).
Here's a chart of the speed for the month of March:
Posted by: jmknapp Feb 15 2006, 02:28 PM
PS: Does anyone know what the field-of-view and resolution of the ONC are?
Posted by: djellison Feb 15 2006, 02:35 PM
http://bookstore.spie.org/index.cfm?fuseaction=DetailPaper&ProductId=619857&coden=
The Optical Navigation Camera (ONC) is part of NASA's Mars Reconnaissance Orbiter (MRO) scheduled for an August 2005 launch. The design is a 500 mm focal length, F/8.3 Ritchey-Chretien with a refractive field corrector. Prior to flight, the off-axis performance of the ONC was measured at visible wavelengths in the off-axis scatter facility at the Space Dynamics Laboratory (SDL). This unique facility is designed to minimize scatter from the test setup to prevent data corruption. Testing was conducted in a clean room environment, and the results indicate that no detectable contamination of the optics occurred during testing. Measurements were taken in two time frames to correct an unanticipated stray light path, which occurred just outside of the sensor's field-of-view. The source of the offending path was identified as scatter from the edges of the field corrector lenses. Specifically, scatter from the interface between the flat ground glass and polished surfaces resulted in significant "humps" in the off-axis response centered at ± 1.5°. Retesting showed the removal of the humps, and an overall satisfactory performance of the ONC. The troubleshooting, correction, and lessons learned regarding the above stray light path was reported on in an earlier paper. This paper discusses the measurement process, results, and a comparison to a software prediction and other planetary sensors. The measurement validated the final stray light design and complemented the software analysis.
Very little info out there though. That's about all I could find.
Posted by: jmknapp Feb 15 2006, 03:52 PM
Very little info out there though. That's about all I could find.
Thanks! That paper states that the FOV is 2.8 degrees (+/- 1.4 degees from the optical axis). I can see from the pointing (CK) SPICE kernels for the last few days that they are indeed periodically slewing the ONC across the position of Mars and Phobos/Deimos. Here's one predicted view from a few days ago:
The targets are in the FOV for about a minute. I gather from the paper that the intent is to have Mars outside the FOV for the science observations.
Posted by: Bob Shaw Feb 15 2006, 07:29 PM
From the MRO website:
http://mars.jpl.nasa.gov/mro/mission/sc_instru_optical.html
"Optical Navigation Camera
This camera is being tested for improved navigation capability for future missions. If it performs well, similar cameras placed on orbiters of the future would be able to serve as high-precision interplanetary "eyes" to guide incoming spacecraft as they near Mars.
From 30 days to 2 days prior to Mars Orbit Insertion, the spacecraft will collect a series of images of Mars' moons Phobos and Deimos. By comparing the observed position of the moons to their predicted positions, relative to the background stars, the mission team will accurately determine the position of the orbiter in relation to Mars.
While not needed by Mars Reconnaissance Orbiter to navigate to Mars, the data from this experiment will be used to demonstrate that this technique can be used by future spacecraft to ensure their accurate arrival. Accuracy is important to some future landers and rovers that will need extremely precise navigation at Mars arrival to get to their landing sites safely."
So, some interesting images of the moons, perhaps?
Bob Shaw
Posted by: jmknapp Feb 16 2006, 03:35 PM
I made an animation of the approach through the first orbit:
http://cboh-t.cboh.org/~jmk/mromoi_snd.mpg
It's from the point of view of a (fictitious) nadir-pointing camera with the same FOV (1.14 degrees) as HiRISE.
Posted by: djellison Feb 16 2006, 03:46 PM
Given the addition of some post-moi-pre-aerobraking imaging, at what appears to be between about 0000 and 0600 on the 15th of March - any idea on a nadir target for that sort of time?
Doug
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Posted by: jmknapp Feb 16 2006, 05:00 PM
Doug
Looks like it's the north polar ice cap. Here's the view midway in that interval (+ marks the nadir point):
Note that the FOV above is 5 degrees. CTX has an FOV 0f 6 degrees; HiRISE 1.14 degrees.
Posted by: Sunspot Feb 16 2006, 05:15 PM
I kept reading that they wouldn't be doing any imaging until after aerobraking was complete.. this is good news.
Posted by: mcaplinger Feb 16 2006, 05:34 PM
Try looking (hint, hint) closer to 6:00 UTC.
Posted by: jmknapp Feb 16 2006, 06:03 PM
Hmmm... here is the view at 0600:
Wondering what you are hinting at--perhaps this is targeted after one of the proposed Phoenix landing sites? The subpoint above is 75N 141W.
Posted by: helvick Feb 16 2006, 06:30 PM
Possibly - I had a placeholder for Phoenix @ 70N 120W but I'm not sure where I got that from. I didn't think the precise landing site had been chosen yet though.
Posted by: Phil Stooke Feb 16 2006, 06:49 PM
It wouldn't be targeted, just whatever they are seeing as they pass by.
Phil
Posted by: babakm Feb 16 2006, 07:05 PM
Some imaging of Phoenix candidate site D is on the MSSS site (roughly 71N 115-120W). The closest image I could find to 75N 141W is http://www.msss.com/moc_gallery/r22_s04/images/R22/R2200441.html, but your nadir looks like it's ~180 degrees away from the projection http://www.msss.com/moc_gallery/r22_s04/mc01.html. Different coord systems?
Posted by: RNeuhaus Feb 16 2006, 07:10 PM
Below is the Sout Pole Cap that looks different than the Nort Pole Cap. The MRO will orbit around poles? 
A much better resolution and visibilty is below: 
This is the south polar cap of Mars as it appeared to the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) on April 17, 2000. In winter and early spring, this entire scene would be covered by frost. In summer, the cap shrinks to its minimum size, as shown here. Even though it is summer, observations made by the Viking orbiters in the 1970s showed that the south polar cap remains cold enough that the polar frost (seen here as white) consists of carbon dioxide. Carbon dioxide freezes at temperatures around -125° C (-193° F). Mid-summer afternoon sunlight illuminates this scene from the upper left from about 11.2° above the horizon. Soon the cap will experience sunsets; by June 2000, this pole will be in autumn, and the area covered by frost will begin to grow. Winter will return to the south polar region in December 2000. The polar cap from left to right is about 420 km (260 mi) across
Rodolfo
Posted by: brianc Feb 16 2006, 08:00 PM
A nice article about the MRO HIRISE camera system here
http://www.phim.unibe.ch/pig/HiRISE_IAF55.pdf
Posted by: mcaplinger Feb 16 2006, 10:14 PM
I think your software is confused, or ours is. What SPICE kernel are you using?
Posted by: jmknapp Feb 16 2006, 10:42 PM
Could be. Here are the kernels I'm using:
CK:
'$KROOT/ck/DESAT_MOI_sc_20060103171803.bc',
SPK:
'$KROOT/spk/spk_c_tcm1-od006_050812_060315_p-v1.bsp',
'$KROOT/spk/spk_moi_lowperf_t2_051123_060320_p-v1.bsp',
'$KROOT/spk/spk_moi_ideal_051123_060320_p-v1.bsp',
'$KROOT/spk/spk_moi_highperf_t1_051123_060320_p-v1.bsp',
I notice there's a big difference whether highperf, ideal or lowperf is used, so maybe that's the difference. The projection above uses highperf (since it's the last listed in the config file).
Posted by: mcaplinger Feb 16 2006, 11:31 PM
We were doing this planning several weeks ago, so the kernel I used was from mid-January. In those kernels, we were near periapsis at 6:00 UTC. Looks like we're looking at some replanning if the MOI performance makes this much difference. I would try rerunning with ideal and see what that looks like.
BTW, what software are you using for this?
Posted by: jmknapp Feb 17 2006, 02:00 AM
BTW, what software are you using for this?
Hmmm... using the "ideal" kernel gives periapsis on 15MAR2006 at 06:24UTC, 399km, at 67S 28E, although it's on the night side so the picture is dark. Pretty big difference there.
The software I'm using is a C program that I wrote to use the CSPICE library--so there could be a bug or three there. The same program works pretty well with Cassini, but at least in that case I have actual images to compare against for testing. Choice of kernels seems to be a big factor.
One kernel tells a cautionary tale:
spk_nomoi_051123_060320_p-v1.bsp
No MOI--gulp! That pessimistic kernel gives this view on 15MAR:
Posted by: mcaplinger Feb 17 2006, 04:05 AM
The software I'm using is a C program that I wrote to use the CSPICE library--so there could be a bug or three there. The same program works pretty well with Cassini, but at least in that case I have actual images to compare against for testing. Choice of kernels seems to be a big factor.
That result sounds pretty close to ours, so I'd say your code is working well. Those kernels just appeared on the NAIF website and I don't know what sort of burn performance differences they represent; it would surprise me if plausible burn variations would change the orbit timing so much.
Posted by: Bob Shaw Feb 17 2006, 12:18 PM
Guys, can you *please* work out whoever is right, you're beginning to (gulp) worry me! MOI has already eaten several pretty toys...
Bob Shaw
Posted by: djellison Feb 17 2006, 12:47 PM
Thing is - only a tiny tiny change in the altitiude at MOI, and the duration of MI will produce quite a large change at aphelion (it's a very eliptical orbit) and so a tiny fraction of a change to either of those numbers, will put quite a different bit of Mars under the spacecraft 5 days later
Doug
Posted by: AlexBlackwell Feb 17 2006, 06:13 PM
You think Mike might be using metric figures, while jmknapp is using English units?
Hmm. That sounds vaguely familiar.
Posted by: jmknapp Feb 17 2006, 06:28 PM
Hmm. That sounds vaguely familiar.
I tend to prefer pixels per fortnight.
Be that as it may, any non-hyperbolic insertion orbit that doesn't intersect the surface is a good one.
Posted by: AlexBlackwell Feb 17 2006, 06:34 PM
That might be why the MRO mission designers baselined for aerobraking instead of lithobraking
Posted by: elakdawalla Feb 17 2006, 06:36 PM
I was going to crack that joke but I thought "Naw -- it's too old and tired." I guess no joke is too old and tired for an academic
--Emily
Posted by: AlexBlackwell Feb 17 2006, 06:50 PM
--Emily
Yeah, the joke was pretty stale.
In fact, as Mike has pointed out over the years, the public has gotten an incomplete if not distorted view of the MCO/MPL/DS2 losses, mainly that the root causes, especially of the MCO loss, can't be simply described as "Oh, they screwed up because they didn't know the difference between metric and English units."
For balance, I would also recommend the following:
Euler, Edward A., Steven D. Jolly, and H.H. Curtis; The Failures of the Mars Climate Orbiter and Mars Polar Lander: A Perspective From the People Involved; AAS 01-074, 24th Annual AAS Guidance and Control Conference, Breckenridge, CO, January 31-February 4, 2001.
A few years ago, Steve Jolly (of LMAO) also sent me some PowerPoint slides, prepared, I believe, for a subsequent conference. These offered some nice perspective, as well as being pretty instructive.
* EDIT - Before "[f]or balance" above, I should have inserted "In addition to the 'official' mishap investigation reports, which can downloaded, among other places, http://discovery.larc.nasa.gov/lessonslearned.html, as well as the popular press coverage (of varying degrees of accuracy),..."
Posted by: Phil Stooke Feb 17 2006, 06:58 PM
Emily: "I guess no joke is too old and tired for an academic"
And no academic is too old and tired for a good joke.
Phil
Posted by: mcaplinger Feb 17 2006, 07:50 PM
Very funny, Alex.
If it makes anyone feel better, I don't have anything to do with planning MOI.jmknapp has performed a valuable public service by highlighting that those three kernels produce significant orbital timing changes; I hadn't appreciated that the MOI performance could induce that large a change, but now we're prepared. We weren't given any context about what those kernels might mean -- they just showed up on the NAIF website. They may be for training purposes, or they may be physically realistic.
Posted by: lyford Feb 17 2006, 08:06 PM
And no academic is too old and tired for a good joke.
Phil
And I was going to crack that joke.....
It's getting to the point where I log on to UMSF and just nod in assent to almost every post
Posted by: AlexBlackwell Feb 17 2006, 08:06 PM
If it makes anyone feel better, I don't have anything to do with planning MOI.I couldn't resist the tweak, Mike, especially since I know the way the MCO/MPL/DS2 losses were reported has grated on you. It's not the same, though, as needling Bruce. Now that is fun
Is this similar to the slight differences between MSSS-generated and JPL-designed targeting boxes that were evident early in MOC campaign? If I remember correctly, sometimes your orbit predicts disagreed with JPL's.
Posted by: djellison Feb 17 2006, 08:09 PM
Now that's actually a requirement for membership here, it's not a matter of humour - it's part of the process
Doug
Posted by: jmknapp Feb 17 2006, 09:39 PM
FWIW, here's the difference between the three kernels in terms of altitude. Looks like they are very different. Not sure of the context as you say--both high perf and low perf have shorter periods than ideal.
Posted by: djellison Feb 17 2006, 09:59 PM
Being VERY unscientific, approx speed at periareion using Orbiter with these apareion's....
10000km - 4330 m/sec
18000km - 4460 m/sec
28000km - 4590 m/sec
38000km - 4650 m/sec
45000km - 4670 m/sec
So to vary between 28000 and 45000 is only a 80ish m/sec difference, in an MOI burn of I believe roughly 1000 m/sec over 25 minutes - so +/- 40m/sec is about a 4% error, or 1 minute of the burn
200 x 400km orbit is approx 3520 - 3320 m/sec ish -so aerobraking is giving us another 1000 m/sec of delta V.
All figures very VERY roughly done in orbiter.
Doug
Posted by: AlexBlackwell Feb 17 2006, 10:25 PM
Feb. 17, 2006
Dwayne Brown/Erica Hupp
Headquarters, Washington
(202) 358-1726\1237
Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.
(818) 354-6278
MEDIA ADVISORY: M06-029
NASA ANNOUNCES MARS MISSION BRIEFING
NASA will brief news media about the Mars Reconnaissance Orbiter
mission at 1 p.m. EST, Friday. The event is in NASA's auditorium, 300
E Street SW, Washington.
The NASA spacecraft is scheduled to arrive at Mars on March 10, 2006.
It will provide more information about the planet than all previous
NASA Mars missions combined. Participants will address mission goals
and the sequence of events necessary to successfully place the
vehicle into orbit around Mars.
Briefing Participants: Doug McCuistion, NASA Mars Exploration Program
Director, NASA Headquarters; Michael Meyer, NASA Mars Lead Scientist,
NASA Headquarters; James Graf, Mars Reconnaissance Orbiter Project
Manager, Jet Propulsion Laboratory, Pasadena, Calif.; Bob Berry,
Director, Space Exploration Systems, Lockheed Martin Space Systems
Co., Denver.
The briefing will air live on NASA TV, and the panel will take
questions from reporters at participating NASA centers. To ask phone
questions, reporters must call Jet Propulsion Laboratory media
relations by 5 p.m. EST, Tuesday at: (818) 354-5011 to obtain a
call-in number. To view a live webcast of the event and for more
mission information on the Web, visit: http://www.nasa.gov/mro
NASA TV's Public, Education and Media channels are available on an
MPEG-2 digital C-band signal accessed via satellite AMC-6, at 72
degrees west longitude, transponder 17C, 4040 MHz, vertical
polarization. In Alaska and Hawaii, they're on AMC-7 at 137 degrees
west longitude, transponder 18C, at 4060 MHz, horizontal
polarization. For digital downlink information on the Web, visit:
http://www.nasa.gov/ntv
-end-
Posted by: Bob Shaw Feb 17 2006, 10:46 PM
The way I see it, almost *any* orbit is better than an unplanned landing mission. And I was, originally, really trying *not* to be cruel about the MCO trajectory, honest! I didn't *need* to be cruel, not with you lot aboard...
Bob Shaw
Posted by: AlexBlackwell Feb 17 2006, 10:52 PM
Hey, you forgot to include the appropriate emoticon. Or did you forget?
Posted by: RNeuhaus Feb 17 2006, 10:55 PM
Also don't forget of Mars orbiter Nozomi, the japanese probe passed by 1000km above the Martian surface on December 14 and escaped from the gravitational sphere of Mars on December 16 to continue on traveling along the orbit around the sun. due to unrecoverable malfunction injection.
No more jokes of that kind, no matter of what old is that but not one as a good prediction
. MRO is a very nice toy! Rodolfo
Posted by: ElkGroveDan Feb 17 2006, 11:06 PM
OK now that we have figure out that there are problems with the Colonel's spices, the original question seems to have been lost. What was Mike referring to when he said "Try looking (hint, hint) closer to 6:00 UTC."?
Posted by: dvandorn Feb 18 2006, 12:57 AM
I've been doing that for quite a while... though, of course, there are a few posts every day that I certainly don't assent with. But, hey, as my father always used to tell me, it takes all kinds...
-the other Doug
Posted by: Bob Shaw Feb 18 2006, 01:06 AM
-the other Doug
oDoug:
Was this outbreak of reasonableness PRE or POST medication?
Bob Shaw
Posted by: dvandorn Feb 18 2006, 01:19 AM
I think it's probably safest to blame it all on the pain meds... 
Actually, I don't feel exceptionally different from how I usually feel. A little lightheaded, but that's it. I *think* I'm still pretty sharp and clear when it comes to understanidng what I'm reading and being able to write in a coherent fashion. But y'all let me know if I start acting even more eccentric than normal...
-the other Doug
Posted by: yaohua2000 Feb 19 2006, 01:12 AM
Mars Reconnaissance Orbiter was only 5 million kilometers from Mars at 2006-Feb-18 12:41:54 UTC.
For Mac OS X users, you can download my widget to keep tracking the distance of the spacecraft to Mars on your Dashboard.
Download: http://magicnumber.sourceforge.net/MRO.zip
You can also make this distance as your signature on this forum, for the details, see http://magicnumber.sourceforge.net
Posted by: RNeuhaus Feb 19 2006, 06:14 AM
After reading more details about MRO. I found it many interesting and surprises things:
As Mars Reconnaissance Orbiter approaches Mars traveling about 10,400 km per hour, it will need to fire six main engines for a long 25-minute burn, slowing the spacecraft down by about 3,584 km per hour! That reduction of speed relative to the planet will place the spacecraft into a long looping orbit around Mars.
The same as Doug has told us.
All subsystems and instruments on board (the so-called "dry mass") must weigh less than 1,031 kilograms (2,273 pounds) to allow room for 1,149 kilograms (2,533 pounds) of propellant for trajectory correction maneuvers that keep the spacecraft on target during the cruise to Mars and for burns that help capture the spacecraft into orbit around Mars.
The monopropellant hydrazine tank is big enough to hold 1187 kilograms (2617 pounds) of usable propellant. This amount of propellant, when used, will change the spacecraft's velocity by about 1.4 kilometers per second (3,100 miles per hour). Over 70% of the total propellant will be used during just one maneuver - Mars orbit insertion.
The propulsion combustible takes up more than 50% of spacecraft weigth.
Some way is needed to push the propellant to the thrusters. Mars Reconnaissance Orbiter feeds pressurized helium gas from a separate high- pressure tank, through a regulator, into the propellant tank where it puts the hydrazine propellant under pressure. Then, when any thruster is opened, the propellant will flow rapidly out, much like paint does from a can of spray paint.
Interesting, MRO uses HELIUM GAS to push Hydrazine away from the tank.
Pressurant Tank
About thrusters, a total of 20 rocket engine thrusters are onboard:
* Six large thrusters, each producing 170 Newtons* (38 pounds force) of thrust for performing the Mars orbit insertion burn. Together, all six produce 1,020 Newtons (104.5 kg 230 pounds force) of thrust. That's about the force you would feel if an NFL linebacker decided to sit on you.
* Six medium thrusters, each producing 22 Newtons* (5 pounds force) of thrust for performing trajectory correction maneuvers, and for helping to keep the spacecraft pointing in the right direction during the Mars orbit insertion burn.
* Eight small thrusters, each producing 0.9 Newtons* (0.2 pounds force) of thrust for controlling where the orbiter is pointed during normal operations as well as during Mars orbit insertion and trajectory correction maneuvers.
(*A Newton is a unit of force required to accelerate a mass of one kilogram one meter per second?every second!). One Newton is equivalent to 1.626 kg of push force.
So many thrusters! 20. I tought it had 7!!!
Spacecraft Configurations:
what the spacecraft will look like during various phases of the mission
During aerobraking, the solar panels have a special role to play. As the spacecraft skims through the upper layers of the martian atmosphere, the large, flat panels act a little like parachutes to slow the spacecraft down and reduce the size of its orbit.
The friction from the atmosphere passing over the spacecraft during aerobraking will heat it up, with the solar arrays heating up most of all. The solar arrays have to be designed to withstand temperatures of almost 200 Celsius (almost 400 degrees Fahrenheit!).
MRO will get very hot, up to 200 degree of centigrades at the perigee passing.
At Mars, the two panels together produce 1,000 Watts of power.
Nickel-hydrogen batteries
During each two-hour orbit around Mars the spacecraft will experience a "day" and a "night." During the "night," there is no sunlight because the planet is between the orbiter and the sun, and therefore blocks the sun's light from reaching the spacecraft. Astronauts on the shuttle experience this kind of pattern as well when they orbit the Earth.
During the nighttime periods, batteries are used to provide the necessary electrical power. The batteries charge during each "day" (using part of the electricity produced by the solar cells) and discharge during each "night' to keep the spacecraft supplied with electricity.
Mars Reconnaissance Orbiter uses two Nickel-Hydrogen rechargeable batteries, each with an energy storage capacity of 50 Ampere-hours - at 32 Volts that's 1,600 Watts for one hour. The spacecraft can't use this total capacity, because as a battery discharges its voltage drops. If the voltage ever drops below about 20 Volts then the computer will stop functioning - a very bad thing! So, to be safe, only about 40% of the battery capacity is ever planned to be used.
Comparing to MER, they have 1.2 M˛ of solar panel and its produces about 1000 wats when they had the best atmospheric conditions and about during the summer. The MRO has big solar panels, 10 M˛ and also produces about the same to MER? MRO will orbit Mars every two hours?, somewhat slower than ISS around Earth with 91 minutes.
There are three main mechanisms on board Mars Reconnaissance Orbiter:
* one that allows the high-gain antenna to move in order to point at earth
* two that allow the solar arrays to move to point at the sun
Each of these mechanisms, called gimbals, can move about two axes in much the same way that your wrist allows your hand to move in two axes: left/right and up/down. By contrast, your knee only has one axis of motion, but your neck has three.
As the spacecraft travels around Mars each orbit, these gimbals allow both solar arrays to be always pointed toward the sun, while the high-gain antenna can simultaneously always be pointed at earth.
What advanced is the space orientation software that the information from star tracker and sun sensors are feeding to the software in order to adjust constantly the solar panels and antenna pointing to Sun and Earth respectively.
The solar panels must be strong enough to survive launch, when the forces can exceed 5 g's. This means that the structure must be designed as if the spacecraft weighed five times what it does on earth! Extremely lightweight but strong materials are used to achieve this strength, including titanium, carbon composites, and aluminum honeycomb.
Any commercial airplane can withstand greater than 3 gravity but the military fighters can do up to 8 g's but the airman will be inconcient for that rather time.
Powerfull telecomunications
With its large-dish antenna, powerful amplifier, and fast computer, Mars Reconnaissance Orbiter can transmit data to earth at rates as high as 6 megabits per second, a rate ten times higher than previous Mars orbiters. This rate is quite high considering that Mars Reconnaissance Orbiter will achieve it while 100 million kilometers (62 million miles) from Earth.
Ten times faster than the previous Mars orbiters, which ones? I suppose it is refering to Odyssey?
High-gain Antenna
The high-gain antenna is a 3-meter diameter (10-foot) dish antenna for sending and receiving data at high rates.
The high-gain antenna will be deployed shortly after launch (see launch configuration), and will remain deployed for the remainder of the mission. It will serve as the primary means of communication to and from the orbiter.
The high-gain antenna must be pointed accurately and is therefore steered using the gimbal mechanism.
Low-gain Antennas
Two smaller antennas are present for lower-rate communication during emergencies and special events, such as launch and Mars Orbit Insertion. The data rate of these antennas is lower because they focus the radio beam much more broadly than the high gain antenna, so less of the signal reaches earth. But the Deep Space Network station on the earth can "see" the signal even when the spacecraft is not pointed at earth, and this is why these antennas are useful for emergencies. Think of how a flashlight works: with a tightly focused beam of light you can see farther directly ahead but not at all to the side. And with a wide beam you can see all around you but not very far. The low-gain antennas have the capability to transmit and receive.
The two low-gain antennas are mounted on the high-gain antenna dish - one on the front side and one on the back -- and are moved with it, although as just mentioned they do not require accurate pointing. Two are needed in that placement so that communication is possible at all times, no matter what the position of the spacecraft might be at a given time.
MRO has two LGA (front and back) and it has very good redundancy comparing to one of Hayabusa.
Mars Reconnaissance Orbiter uses a monopropellant propulsion system: there is fuel (hydrazine), but no oxidizer. Thrust is produced by passing the fuel over beds of catalyst material just before it enters the thruster, which causes the hydrazine to combust . (Other types of systems use bipropellant propulsion, where combustion is achieved by mixing a fuel with an oxidizer. The Space Shuttle, for example, uses liquid hydrogen as fuel and liquid oxygen as oxidizer, which spontaneously combust (explode) when they are mixed.)
Propellent: It is monopropellent. ONLY one : HYDRAZINE. It is a fuel. It does not need oxygen as an oxidizer to ignite. What is the catalyst material that causes the hydrazine to be fueled. 
Electrical ignition?
Reaction wheels:
While the reaction control system thrusters allow the spacecraft to turn quickly, they're not good at slow and steady turns. Slow and steady turns, however, are just what is required to take high-resolution images of Mars from orbit. Mars Reconnaissance Orbiter therefore has devices called reaction wheels. These are literally spinning wheels - four in total: one for each rotational axis plus a spare in case one of the three isn't working.
Good ones: 4 reactions wheels: one for three dimension axis plus one as a spare. Even better than Hayabusa.
Spacecraft Parts: Command and Data-Handling Systems
The Command and Data Handling subsystem is essentially the "brains" of the orbiter and controls all spacecraft functions. This system:
* manages all forms of data on the spacecraft;
* carries out commands sent from earth;
* prepares data for transmission to the earth;
* manages collection of solar power and charging of the batteries;
* collects and processes information about all subsystems and payloads;
* keeps and distribute the spacecraft time;
* calculates its position in orbit around Mars;
* carries out commanded maneuvers; and,
* autonomously monitors and responds to a wide range of onboard problems that might occur.
Space Flight Computer:
At the heart of the space flight computer, Mars Reconnaissance Orbiter employs the next generation of space-qualified processors, based on the 133 MHz PowerPC processor. While this speed may seem slow compared to the Gigahertz speed of the computer you're using to read this web site, it is fast by space standards. Commercial chips must be significantly enhanced and undergo long duration testing to prove they will survive the unforgiving radiation environment of space.
Flight Software:
The Flight Software is an integral part of the Space Flight Computer, and includes many applications running on top of an operating system, similar to the way your home computer has applications running on top of Microsoft Windows or MacOS. Mars Reconnaissance Orbiter's operating system is called VxWorks.
An example of an application is Fault Protection. Fault Protection continuously monitors hundreds of parts of the spacecraft for a wide range of problems, takes action to fix the problem if it can, and if it can't, keeps the spacecraft safe while it waits for instructions from Earth.
Smart enough to handle by itself during if there is a fault.
Solid State Recorder:
The Solid State Recorder is the primary storage for science instrument data onboard the spacecraft, with a total capacity of 160 Gigabits. That may seem like a lot, but not when you realize that a single image from HiRISE can be as big as 28 Gigabits!
The science data is stored on this recorder until it is ready for transmission to Earth, and then is overwritten with new science data.
The recorder is called a Solid State Recorder because it has no moving parts. Neither a tape recorder nor a hard disk drive, this device uses an array of over 700 memory chips, each with 256 Megabit capacity, to store Mars Reconnaissance Orbiter's data.
Whopping storage capacity in solid state record (RAM). The big computers has that amount storage. There very few computers have it.
Sensors
Sensors determine where the spacecraft is pointed, how fast it is turning, and how its speed is changing. They include:
sun sensors:
Sixteen sensors (eight are backups) deployed around the spacecraft body provide knowledge of where the sun is located. These sensors are pretty simple, and only give two answers: "I see the sun" or "I don't see the sun." The computer and flight software listen to all of the sensors and can deduce where the sun is from that information. Since the spacecraft relies on sunlight to create electrical power, this function is very important.
The sun sensors normally are used only when first waking up the spacecraft (for example, after launch) and during spacecraft emergencies - in both cases the spacecraft may not know where it is pointed.
The sun sensors give enough information so the spacecraft can continue to get power from the sun, but they don't give enough information for other things, like finding the earth, or a spot on Mars. For that, more sophisticated sensors coupled with computer software are required (see below).
Two star trackers are used to provide full knowledge of the spacecraft orientation, allowing the spacecraft to know not only where the sun is, but also where Earth and Mars are and how to point to any direction in the sky (which is necessary when doing a maneuver). As is the case with many components aboard Mars Reconnaissance Orbiter, the second star tracker is there as a back-up in case the first one fails.
The star tracker is a very smart camera. The star tracker takes a digital picture of the stars. Then, using its own catalog of thousands of stars, it compares the image with the catalog until it can identify the stars in the image. Once it does that, it knows exactly where it was pointing when it took the picture, and it sends a message to the computer with that information. And it does that ten times every second!
So many Sun sensors!!! up to 16??? (8 for backups) MRO has two star trackers which help to spacecraft ot only to know where the sun is located but also of Earth and Mars.
Sorry of that long post. It will permit us to be much better prepared to understand better of any MRO directions, movements, timing, so that we can discuss it better.
Rodolfo
P.D. More details, visit http://mars.jpl.nasa.gov/mro/mission/sc_parts.html
Posted by: The Messenger Feb 19 2006, 06:35 AM
Nice collection of details. Hydrazine (HN#NH) has been the fuel-of-choice for vectoring motors since Minuteman, which also uses the helium replacement system (The helium is stored in donuts wrapped around the nozzles, both cooling the nozzles and heating the replacement gas.) A monofuel allows simple valve trains and combustion chambers. Hydrazine is both toxic and corrosive - not surprising, as are most highly reactive chemicals.
Posted by: dilo Feb 19 2006, 07:50 AM
Thanks for resuming all these infos, Rodolfo (perhaps the biggest post I saw in the Forum...).
A couple of considerations on the data storage/transmission.
They say: "Over its two-year primary science mission, the spacecraft is predicted to transmit more than 34 Terabits-that's more than all the data transmitted by all previous JPL spacecraft put together!"
This means an average transmission of 0.54 Mbit/sec if spacecraft is continuosly transmitting (obviously this is not true due to occultation and multiple DSN tasks); this figure is about one eleventh of real MRO antenna data rate (at 100 million Km).
Moreover, is a single image require 28 Gbit, this means only slightly more than 1000 images transmitted during primary mission, about 1.5 images/day...
I know we already spoken about bandwith bottleneck, this is just a remind... 
Posted by: djellison Feb 19 2006, 09:32 AM
[quote name='RNeuhaus' post='42269' date='Feb 19 2006, 06:14 AM']
Interesting, MRO uses HELIUM GAS to push Hydrazine away from the tank.
Pressurant Tank
[/quote]
I think just about every spacecraft I've ever seen does this.
[quote]
So many thrusters! 20. I tought it had 7!!!
[/quote]
Well - 7 main ones for the engine burn for MOI - but then lots of smaller ones for smaller manouvers and rotating the spacecraft to unload gyros.
[quote]
MRO will get very hot, up to 200 degree of centigrades at the perigee passing.
[/quote]
Ah - carefull - they say it's designed to withstand 200 degrees, not that they will nearly reach 200 degrees. They're get warm - but nothing like 200 deg. I think one of the tech papers I mentioned elsewhere shows CFD of how warm it might get.
[quote]
Comparing to MER, they have 1.2 M˛ of solar panel and its produces about 1000 wats when they had the best atmospheric conditions and about during the summer. The MRO has big solar panels, 10 M˛ and also produces about the same to MER? MRO will orbit Mars every two hours?, somewhat slower than ISS around Earth with 91 minutes.
[/quote]
Ahh - again, no - MER can produce up to about 1000 Watt-HOURS per sol, i.e. the equiv of 100 watts for 10 hours. Typically, the MER solar arrays would rarely produce more than 100 Watts at any one time - I'm not sure of the exact figures.
[quote]
Ten times faster than the previous Mars orbiters, which ones? I suppose it is refering to Odyssey?
[/quote]
and then some....
The very highest data rate I've seen quoted for Odyssey is 124425 bits per second - i.e. roughly 0.125 Mbits/sec
MRO's still a bit fluffy on quoted numbers - but the highest it can do is certainly around 5 Mbits/sec.
[quote]
Good ones: 4 reactions wheels: one for three dimension axis plus one as a spare. Even better than Hayabusa.
[/quote]
And the same as Cassini - which is already using its spare.
[quote]
Smart enough to handle by itself during if there is a fault.
[i]
[/quote]
Same as most spacecraft really.
[quote]
Whopping storage capacity in solid state record (RAM). The big computers has that amount storage. There very few computers have it.
[/quote]
Well - 160 Gbits is about 20 Gigabytes - and onboard that is equiv to the 'hard drive' for MRO - and I think we'd all be moaning if we only had that
Doug
Posted by: deglr6328 Feb 19 2006, 10:46 AM
Electrical ignition? Hydrazine explodes on contact with many common metal oxides. Found this: "Most hydrazine thrusters use a catalyst bed made from iridium impregnated alumina (Al2O3) pellets 1.5 to 3 mm in diameter."
Posted by: helvick Feb 19 2006, 10:57 AM
and then some....
The instantaneous peak output of the MER Panels at mars would vary between ~146 and 214watts if they were in orbit rather than on the surface. Taking the atmosphere and seasonal Tau into account that changes to ~140 to 164 watts.
I thought MRO had 2x10m^2 panels which could peak at between 2.2 and 3.3kw but I presume that they are rarely optimally oriented so an average of 1000 watts over each orbit is probably right.
Posted by: Airbag Feb 19 2006, 07:26 PM
Another interesting tidbit - MRO uses the same X-band uplink/downlink channel (32) as Spirit...an unexpected problem relating to Spirit's longevity. Expect to see much more UHF commanding of Spirit via Odyssey in the near future. Opportunity's channel (29) is shared with Deep Impact, but that has not been an issue so far because of their spatial separation.
Airbag.
Posted by: Bob Shaw Feb 19 2006, 09:41 PM
Airbag.
Am I alone in thinking that this is, er, silly? Or was it too expensive to change the ground station gear?
Bob Shaw
Posted by: Myran Feb 19 2006, 11:03 PM
It doesnt sound like good planning to me. Not that I am as singleminded to think that any command from Earth intended for MRO will make Oppertunity to attempt spinning its nonexistant flywheels, or MRO to start evasive manuvers to avoid dangerously soft dunes.
Yet there could be a potential problem if any or both are programmed to stop and recieve when they catch a signal from Earth, and so might stop whatever work they do when the commands actually are for the other one. Are this a risk or do they really go completely 'mute' when they execute the set of commands they have gotten previously?
Posted by: djellison Feb 19 2006, 11:07 PM
I imagine that a spacecraft that notices a signal on it's own channel, but can't understand it ( which is quite likely given the different bit rates the two spacecraft would be commanded with ) would probably go into a safe mode under the assumption that there is something wrong.
Doug
Posted by: Steve Feb 19 2006, 11:27 PM
Doug
Assuming intelligent design among the engineers at JPL (the pun was unintentional, but irresistable) can't we assume that they have a way to turn off Sprit's receiver when they plan to send signals to MRO and vice versa.
Steve
Posted by: Bob Shaw Feb 19 2006, 11:40 PM
Steve
Steve:
Please don't put that sort of idea into their heads!
Bob Shaw
Posted by: djellison Feb 19 2006, 11:42 PM
I was thinking that, I imagine they can sequence things whereby the two dont listen in on one another, but there's still scope for cross talk at some point. For UHF commanding, as I understand it, you have quite a big latency, as they don't uplink to Odyssey as often as they would want to uplink to Spirit.
Doug
Posted by: belleraphon1 Feb 20 2006, 12:51 AM
Airbag.
Also.... these engineering decisions are made long before launch.... it is possible that no one anticipated Spirit still being functional in 2006.
Craig
Posted by: edstrick Feb 20 2006, 06:08 AM
On it's second lunar day, JPL tried to get Surveyor 6 to wake up and transmit. Surveyor's 1 and 5 had operated successfully on the second (and for 5, later) lunar days, despite cold damage.
Surveyor 6 transmitted signal briefly, then went silent. While they were attempting various commands, switching systems in the blind, Surveyor 1 (which had the same receiver frequency) woke up instead on it's 7'th lunar day and briefly transmitted. I don't recall for sure, but I don't think they got interpretable telemetry from either of them during the attempts.
Surveyor 7 also was successfully operated during it's second lunar day.
Lunar Orbiter 1 was deliberately crashed at the end of it's extended mission to clear up a communications frequency.
Posted by: ugordan Feb 20 2006, 08:27 AM
Don't the DSN uplink commands have a sort of digital signature as well as intended receiver "address" in their packet headers so that Spirit/MRO know the transmission is directed towards them specifically?
That would sure seem a logical and sensible thing to do. What would otherwise prevent, say, ESA's New Norcia DSN station to "accidentally" transmit garbage on channel 32 and screw up both probes at once?
Posted by: edstrick Feb 20 2006, 08:46 AM
I think we're dealing with paleolithic technology standards, maybe from the 70's or 80's.
<grin>
Posted by: Airbag Feb 20 2006, 07:22 PM
<grin>
Perhaps, but the Small Deep Space Transponders are new technology and used by many current missions. There are only so many X-band channels and they are simply all used up. This is all from the DESCANSO MER telecoms report (very interesting reading I thought).
The spacecraft do have their own IDs, but best not to tempt fate with multiple bit errors etc. and perhaps accidentally accept and decode a command not intended for that spacecraft. And yes, that can happen - Opportunity accidentally went into safe mode during a solar opposition experiment in which a bunch of NOPs was changed into something else as multiple bit errors slipped by the error checking etc.
There are several techniques (other than the obvious one of using Mars itself as a "blocker") that can be used to make sure X-band signals intended for MRO (and that is the important one during aerobraking) only get to MRO. From memory, I can recall these (there were others too):
- Change Opportunity's antennas' polarization (so that it is opposite to that of MRO)
- Doppler adjustment for specific target
- Reduce transmit power level (MRO has more gain)
Airbag
PS BTW, receivers are typically *never* turned off (except during Opportunity's Deep Sleep).
Posted by: Bob Shaw Feb 20 2006, 10:18 PM
Can I patent interplanetary MAC addresses - they could be stored digitally in a small solid-state pod, perhaps?
We could call, them, oh, iMACs and iPods...
Seriously, if a $10 network card can have a unique identifier burned in, why don't spacecraft?
Bob Shaw
Posted by: Myran Feb 20 2006, 10:40 PM
Of course! If they can do that relatively easy its a good solution. And delegate the problems to the communication engineers then who are more qualified in the first place.
Posted by: helvick Feb 21 2006, 12:08 AM
I had a long boring waffle about bit rate, harmonics, the history of MAC addresses, Ethernet's emergence in the late 1980's and collisions on ARCNET networks in the early 1990's here but re-reading it made my eyes glaze over so I thought it would be better to simply point to the http://public.ccsds.org/default.aspx and in particular the http://public.ccsds.org/publications/archive/133x0b1.pdf as an example of just hom much thought has to go into doing this sort of thing properly.
If only it was as simple as tagging each packet with a 12 byte target identifier.
Posted by: Bob Shaw Feb 21 2006, 11:16 AM
If only it was as simple as tagging each packet with a 12 byte target identifier.
I followed the links, and yes, there's a lot of work been put into the definition of the systems and architecture pertaining to Space Packets and wholly laudable commitments to international and interplanetary interoperability. But nowhere do I see such a thing as an analogue of a MAC address, which has historically provided a more-or-less fail-safe identifier for almost any bit of hardware. I still can't see why not...
...am I missing something?
Bob Shaw
Posted by: helvick Feb 21 2006, 02:19 PM
...am I missing something?
Ah I get your point now - why not just have a unique hardware based ID per probe and leave it at that? Use something like a MAC address (12 bytes) so you can be pretty sure you'll never get a collision.
I don't think that the identity is the problem and that's all a MAC type idea will give you - an assured unique identity to enable specific devices to extract their data from a shared transmission medium. The spacecraft all have adequately unique identifiers at the moment in any case so the two main problems are firstly whether they are included in the command data packets that are transmitted at the moment and secondly if they are then what sort of error handling is in place to ensure that cross talk doesn't happen? Multiple bit flip errors seem to have made it possible for one asset to incorrectly intepret a signal intended for a different asset in the past so it would seem that the error codes being used by the MER's are not 100% perfect.
Another problem is just overall congestion of the system. If there is some need for complicated command sequencing on MRO and MER at the same time then one or other will have to back off in order to allow the other to finish.
Posted by: mcaplinger Feb 21 2006, 02:39 PM
See the Global Spacecraft ID document: http://public.ccsds.org/publications/archive/320x0b1s.pdf
Of course, these are only 8 or 10 bits long.
But has been already pointed out, just relying on an ID field to reject commands would be foolish in the presence of bit errors. If you were designing a mission-critical system based on Ethernet (which probably wouldn't be a good idea anyway because of single point failures in the shared transmission medium) you would hopefully not rely on MAC uniqueness to keep the wrong receiver from doing something. It might be unlikely for a burst of errors to corrupt one MAC address into another in such a way to get past CRC checking, but it's not "fail-safe". Even with your home LAN, there are acknowledgement protocols in TCP/IP to keep such problems from happening.
Posted by: djellison Feb 21 2006, 03:27 PM
As I understand it - spacecraft are all moving very quickly in different directions, so there is dopler to worry about, and they are scheduled to listen at particular upilnk rates, and so on and so forth.
If MRO's listening to it's uplink at X bps, and it's being sent at Y Hz off the specified frequency, it may be that Spirit interprets that as a bad uplink as it was expecting W bps and is moving in a way that is Z Hz of specified wavelength.
I'm fairly sure they'll be able to sequence things intelligently to sort this problem out.
Doug
Posted by: Toma B Feb 24 2006, 07:47 AM
Is there any planed imaging with HiRISE on approach to Mars?
If not, why not?
Posted by: ugordan Feb 24 2006, 08:06 AM
There's always a good reason for not performing observations shortly before orbit insertion. The latter is such a critical maneuver that the spacecraft team doesn't want to take any chances that might jeopardize the entire mission. When you use the instruments on board, they can always report a fault state due to various reasons and cause the S/C to go into safe mode which will then obviously just sit around and wait to hear from Earth.
Obviously, if a safing event happened shortly before orbit insertion the whole mission could go down the drain. That's why we typically get imaging after the maneuver and only on some missions a very distant image of the target well before the arrival.
Posted by: djellison Feb 24 2006, 08:27 AM
--><div class='quotetop'>QUOTE(Toma B @ Feb 24 2006, 07:47 AM) </div><div class='quotemain'><!--quotec-->
Is there any planed imaging with HiRISE on approach to Mars?
If not, why not?
[/quote]
Not that I know of - because the optical navigation camera is not boresighted with HiRISE and needs to be aimed in that direction.
(ONC is the silver thing on the near side of the spacecraft - http://mars.jpl.nasa.gov/mro/gallery/spacecraft/images/MRO_in_LMA_pre-launch.jpg )
Doug
Posted by: Sunspot Feb 24 2006, 09:38 AM
The same was done with Cassini during the week or so before orbit insertion.
Posted by: AlexBlackwell Feb 24 2006, 04:35 PM
The MRO arrival press kit is now up:
http://www.jpl.nasa.gov/news/press_kits/mro-arrival.pdf
posted Feb. 24, 2006 (984 Kb)
Posted by: djellison Feb 24 2006, 04:53 PM
And the press conf is in an hour and a bit as well
Doug
Posted by: jmknapp Feb 25 2006, 03:29 PM
One item from the press conference: other than the test images on March 14, there will be no images during the entire aerobraking phase--the instruments will be on "survival heaters" and the electronics will not be exercised at all.
Posted by: mcaplinger Feb 26 2006, 06:06 PM
"The three cameras from the science payload -- the High Resolution Imaging Science Experiment, the Context
Camera, and the Mars Color Imager -- will take their first test images of Mars as the orbiter passes low over the southern hemisphere near the end of the third orbit, on March 14."
Now that the press kit has let this out of the bag, I'll note that the timing and location moved by ~2 hours and ~30 degrees of longitude between the mid-January predict and the most recent one -- so the imaged areas will be in the southern hemisphere, but we probably won't know exactly where until after MOI.
I don't know yet when we can expect to have the image data back.
Posted by: RNeuhaus Feb 26 2006, 06:27 PM
The MRO spacecraft will remain out of contact for a half hour. Lots of time of suspense. There will be a TV NASA coverage during this MOI?
The 109 km, I think it is the outside of ending of Martian atmosphere. Isn't it?
Rodolfo
Posted by: edstrick Feb 27 2006, 07:10 AM
With apollo, for both orbit insertion and trans-earth-insertion burns, there were 2 important times. The times of expected AOS <acquisition of signal>times: for 1.) if the engine burn did not occur, and for 2.) If the engine burn did occur.
On orbit insertion, a no-burn signal would be early.. an improper burn later, a nominal burn at a specific time.. and an overburn or kablooie if no signal shortly after the optimum burn time.
On TEI, a nominal burn gets you back into view early, as you've sped up in orbit.
To some extent, the same will apply here. If AOS is within a few tens of seconds of the expected time, it's likely we're in a good orbit.
Posted by: jmknapp Feb 27 2006, 03:32 PM
Does anyone know which DSN stations and/or other facilities will be listening for MRO's signal as it emerges from behind Mars at 22:16UTC on March 10th? Which one will likely be the first to report the signal?
Posted by: The Messenger Feb 27 2006, 04:17 PM
The 109 km, I think it is the outside of ending of Martian atmosphere. Isn't it?
Rodolfo
According to the press release, they will be monitoring live on NASA TV. 109 km is cutting it a little close to Mar's fickle atmosphere - I think this is near the final projected path of the Mars Climate Orbiter, but it actually went in somewhere between 95-80 km...
Posted by: Bob Shaw Feb 27 2006, 04:21 PM
Rodolfo
Rodilfo:
Not at all. Relatively speaking, the upper atmosphere of Mars extends *further* from the planet than does that of the Earth, and the pressure drops more slowly. So 109 km is well within the (very thin) upper atmosphere. Mars is particularly good for aerobraking, having a thin but extensive atmosphere which should be more forgiving than our own. But, after MCO and Mars Observer, there will be a certain tension in the (rarefied) air!.
Fingers, and all other appendages should be tightly crossed, chickens should be broken down into component parts, and any spare virgins kept neatly wrapped but ready for sacrifice - it's scawwwwwwy!
Bob Shaw
Posted by: djellison Feb 27 2006, 04:28 PM
Of course - the reason for having such a low targetting point is because a periapsis that low invokes a fast orbital velocity - thus the ammount of engine braking required is less. If they targetted at say, 1500km, the orbital velocity at that altitude would be much slower so requiring much more delta V.
One day - I hope they'll be brave enough for Aero-capture at Mars. It's a very thin line to tred - +/- 10km will give you a bad day one way or the other, but they're getting to the point where it's possible, I'm sure.
Looking at this -
http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=399&vbody=499&month=3&day=10&year=2006&hour=22&minute=15&rfov=60&fovmul=-1&bfov=50&porbs=1&showsc=1
Goldstone will be the primary, with Madrid just setting.
Doug
Posted by: jmknapp Feb 27 2006, 04:50 PM
IIRC, with MER, some secondary facilities (Stanford) were also listening. Wonder if they might do the same with MRO.
Posted by: djellison Feb 27 2006, 04:53 PM
Stanford was listening to MER because MER was also transmitting with its UHF antenna (to MGS), for which Stanford have a good facility, and indeed they caught Spirit, but not Opportunity as I understand it. No such transmission is planned for MRO as I understand it - just X-Band on the LGA which will be for the DSN to grab alone.
Doug
Posted by: mcaplinger Feb 27 2006, 04:54 PM
I think there's some confusion. The aimpoint altitude at MOI is 400 km, not anything lower. After MCO, they're unlikely to try anything much lower.
Posted by: djellison Feb 27 2006, 05:01 PM
Ahh - someone mis-quoted the press pdf previously then - it seemed a bit low to me
Doug
Posted by: Bob Shaw Feb 27 2006, 05:11 PM
Doug
Doug:
I was wondering, too - much lower than MGS!
Let's hope it *doesn't* go low...
Bob Shaw
Posted by: RNeuhaus Feb 27 2006, 07:07 PM
I am thinking about why any of three present Mars Orbiters, ODY, MGS and MEX aren't capable as a relay of any signal from a new member MRO to Earth and viceversa? The rovers might be the witnesers with their PANCAM. Not sure about its proper localization at the MOI critical moments.
Maybe, the space portal: spaceflightnow is confused. Below is the extract:
To take full advantage of atmospheric braking, the low point of the orbit will be carefully reduced to around 62 miles (100 km). It will be raised, or "walked out," later, with the ultimate goal being a roughly circular orbit with a high point of at most 199 miles (320 km) and a low point as close as 158 miles (254 km) to the surface.
http://www.spaceflightnow.com/mars/mro/060224moipreview.html
Rodolfo
Posted by: mcaplinger Feb 27 2006, 07:46 PM
You're quoting the altitude during aerobraking, not the altitude at MOI, which is much higher.
Posted by: The Messenger Feb 27 2006, 07:53 PM
Maybe, the space portal: spaceflightnow is confused. Below is the extract:
To take full advantage of atmospheric braking, the low point of the orbit will be carefully reduced to around 62 miles (100 km). It will be raised, or "walked out," later, with the ultimate goal being a roughly circular orbit with a high point of at most 199 miles (320 km) and a low point as close as 158 miles (254 km) to the surface.
http://www.spaceflightnow.com/mars/mro/060224moipreview.html
Rodolfo
Originally, a lower final orbit (150km) was planned, but they raised it. I am confused enough now that I don't know if they raised it to 300 or 400 km. From Neuhaus' earlier post on this thread:
"Spacecraft Configurations:
During aerobraking, the solar panels have a special role to play. As the spacecraft skims through the upper layers of the martian atmosphere, the large, flat panels act a little like parachutes to slow the spacecraft down and reduce the size of its orbit.
The friction from the atmosphere passing over the spacecraft during aerobraking will heat it up, with the solar arrays heating up most of all. The solar arrays have to be designed to withstand temperatures of almost 200 Celsius (almost 400 degrees Fahrenheit!).
MRO will get very hot, up to 200 degree of centigrades at the perigee passing."
This is consistent with an orbital insertion altitude of 109kms, and a final, rounded orbit of 300-400 km. I think the lowest 'safe' insertion altitude for MCO was 85km, so 109kms may be a little iffy...
Posted by: mcaplinger Feb 27 2006, 08:04 PM
The altitude at MOI has little to do with either the aerobraking altitude or the final mapping orbit altitude. These altitudes are:
400 km at MOI (press kit, page 27)
~100 km during aeropass (press kit, page 30)
320 km x 255 km in final mapping (press kit, page 28)
What's so confusing?
Posted by: djellison Feb 27 2006, 08:34 PM
The way some websites have reported it is all screwey - even the normally reliable ones.
Doug
Posted by: The Messenger Feb 27 2006, 09:12 PM
Nothing...if you scroll beyond the 'Other Missions' in the Press release, thanks. An insertion @ 400km is much, much safer than the 109km figure quoted above. That is chillingly close to the Climate Orbiter's planned trajectory.
Posted by: AlexBlackwell Feb 27 2006, 09:21 PM
I don't know if it's been mentioned here or not but http://www.sharad.org has a dedicated web site, which has some interesting documentation.
Posted by: djellison Feb 27 2006, 09:28 PM
Is it just me - or is there some great documentation listed....but not accesable Sort of a wave-candy-infront-of-baby type thing
Doug
Posted by: Bob Shaw Feb 27 2006, 09:44 PM
Hmmm... ...perhaps it's time to mention the old space-dog's proverb:
Go low, you glow!
Bob Shaw
Posted by: AlexBlackwell Feb 27 2006, 10:02 PM
Sort of a wave-candy-infront-of-baby type thing Sorry about that, Doug. I thought only the second "Documentation" link was reserved for team access (i.e., requires a userid and password). It looks as if the first tree is as well.
Posted by: jmknapp Mar 1 2006, 01:18 PM
I generated a view of Earth as MRO comes out of occultation on March 10th, based on the "ideal" NAIF kernel:
The above is in spacecraft time not accounting for speed of light. The signal would get to Earth 11 minutes, 58 seconds later, at 22:16:00 UTC (5:16pm EST) .
Posted by: Bob Shaw Mar 1 2006, 02:06 PM
The above is in spacecraft time not accounting for speed of light. The signal would get to Earth 11 minutes, 58 seconds later, at 22:16:00 UTC (5:16pm EST) .
Now, if only that could be photographed during the aerobraking test image campaign...
Bob Shaw
Posted by: ugordan Mar 1 2006, 02:16 PM
Not to mention there haven't been all that many cameras with a 0.005 degree FOV flown on planetary missions...
Posted by: djellison Mar 1 2006, 02:28 PM
http://hirise.lpl.arizona.edu/HiRISE/images/hirise_params.gif
1.14 degrees for HiRISE - which is just a tiny bit more than this much
http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=399&vbody=499&month=3&day=10&year=2006&hour=00&minute=00&fovmul=1&rfov=1&bfov=30&porbs=1&showsc=1
Doug
Posted by: jmknapp Mar 1 2006, 03:17 PM
Even so, at HiRISE resolution of 1 urad/pixel, Earth being 59 urad (0.0033 deg) across would be ~59 pixels.
Approximately this resolution (blown up to 512 pixels across):
On the Earthrise time for the HGA, I don't suppose that the Mars atmosphere affects the X-band very much?
Posted by: ugordan Mar 1 2006, 03:31 PM
The effect is probably negligible, even more so due to the fact Mars' atmosphere contains virtually no vater wapor.
The above simulated image would in reality be suspended in a thick reddish tint due to the atmosphere, and the whole Earthrise would have to be very carefully timed even if one knew the precise orbit MRO has -- which obviously won't be the case due to varying performance of the engines during MOI. In short, aiming for this KODAKMMT would be very, very hard and the end result wouldn't be all that rewarding.
Posted by: djellison Mar 1 2006, 03:48 PM
I think I'd rather have the "OMFG thank god for that" moment of the earliest possible HGA signal back on earth suggesting a good burn than the kodak moment to be honest.
MGS did take an Earth and Jupiter image some time ago - perhaps in an extended mission, HiRISE could 'do' earth as well, but in the meantime, I want it looking down
Doug
Posted by: ugordan Mar 1 2006, 04:17 PM
Err... surely you mean the latest possible signal back, meaning a better-than-expected burn? The earliest would be if no MOI occured and that would kinda suck, wouldn't it?
Posted by: djellison Mar 1 2006, 04:19 PM
i.e. earlier than if the spacecraft was orientated to take an image during the egress from behind Mars and then had to reorientate for HGA pointing to Earth.
And there's such as thing as the burn being too long - more is not better - it would mean too much fuel useage and thus lost potential for maintaining the lower science orbit.
Doug
Posted by: ugordan Mar 1 2006, 04:24 PM
Oh, I see. Good point.
True, true!
But a slightly better than nominal burn would conceivably reduce the time required for aerobraking. That is, if a slightly less agressive aerobraking strategy isn't selected in that case.EDIT: Is it me, or is the updated forum SW acting kinda funny sometimes w/ regards to quotes?
Posted by: djellison Mar 1 2006, 04:36 PM
No - it's not just you - I'm looking into it - but edited your post manually to sort it out in the mean time
Doug
Posted by: helvick Mar 1 2006, 05:10 PM
Probably true for this shot but I reckon that a shot of Earthrise over the Martian atmosphere that had this sort of resolution would be a stunningly evocotave picture.
Posted by: mcaplinger Mar 1 2006, 05:33 PM
I'm skeptical about that. The relative sizes of Mars and the Earth from martian orbit make an Apollo-style Earthrise picture impossible. And the martian limb is pretty diffuse. With the degree of magnfication required to resolve the Earth, the limb would be huge and probably featureless. I tried to take a "Phobos rising over the limb" image with MOC (see http://www.msss.com/mars_images/moc/2003/06/23/ ) but test images of the limb with the NA were so bad that I quit trying to get the limb and Phobos in the same NA swath (which was hard anyway due to timing and data volume constraints.)
Posted by: JRehling Mar 1 2006, 06:28 PM
Steve
Both receivers are "turned off" when Mars is between them and Earth. It would mean only transmitting to one when the other was in the black, which would be annoying but do-able. Of course, during aerobraking, MRO will spend a lot of time *not* being occulted.
I once had two VCRs (for dubbing) that shared a remote control signal. I used my coffee table to "occult" the one I didn't want to get a signal. I also usually kept one on and one off, so that every power command (no occultation) toggled which one was on.
Posted by: helvick Mar 1 2006, 06:55 PM
Ah well maybe it's a shot that someone will be able to take someday as they look back earthwards on their cruise from Mars to Jupiter:).
Glad to see that such shots are considered at least, even if they turned out to be impractical. I quite like the end result in your link - the two contrasting images really drives home just how good the MOC NA is.
Posted by: JRehling Mar 1 2006, 08:24 PM
Consider the opposite. Could we usefully take a picture from Earth orbit of Marsrise (or Venusrise/Jupiterrise)? From Hubble? From a weather satellite? From a mountaintop? All signs point to "no"! If the pointing and magnification were precisely done, the atmospheric interference would be terrible. I'm not sure what the optical properties of the martian atmospheric column are, but I bet a double horizon-pointing vector with all the dust and that scale height would be pretty bad.
The timing would also have to be exquisite. Forget about color! [I have in my living room that famous silhouette of a tree, an adult, and a child, in front of the full Moon. That picture (if "real"?) would have required exquisite timing itself, but at least only the Moon was moving.]
If I saw someone take a ground-based picture of Jupiterrise on Earth, I'd start to consider the martian Earthrise feasible.
Posted by: Bob Shaw Mar 2 2006, 01:24 PM
Well, what can I say? I spotted that image set ages ago, and really hoped there'd be more of a sequence sometime - it was a great teaser. I hope you realise that there'll now probably be a re-run of the Apollo 8 Earthrise debate, with all your MSS colleagues insisting that they pressed the button, too? Hehe.
Bob Shaw
Posted by: Joffan Mar 2 2006, 07:13 PM
Has anyone heard or found any information on the TCM scheduled for 28 Feb?
Posted by: lyford Mar 2 2006, 08:39 PM
Something like this?
(Apologies if the image is too large - please let me know - I try to keep everything under 100k and 640px wide)
Though I think this shot will be a fantasy for some time to come....
Posted by: The Messenger Mar 2 2006, 09:57 PM
"The third trajectory correction maneuver was deemed unnecessary due to the precision of the spacecraft's current path."
http://mars.jpl.nasa.gov/mro/mission/orbiter_update.html
Posted by: djellison Mar 2 2006, 10:21 PM
The Feb 29th manouver would have been TCM 4, that statement is refering to the half-way-point-ish manouver a few months ago.
Doug
Posted by: yaohua2000 Mar 2 2006, 11:15 PM
MRO is now no more than 2 million kilometers away from Mars.
Mars Reconnaissance Orbiter was 2000000 kilometers away from Mars at 2006-03-02 19:17:59 UTC.
http://www.yaohua2000.org/cgi-bin/New%20Horizons.pl
Posted by: RNeuhaus Mar 3 2006, 02:28 AM
The next suspense time would be:
Times listed in Eastern.
Arrival at Mars
Mar. 10
NASA TV coverage: 3:30 p.m. - 5:45 p.m.
Rodolfo
Posted by: The Messenger Mar 3 2006, 02:52 PM
Doug
http://mars.jpl.nasa.gov/mro/mission/tl_approach_tcm.html
TCM-5: This maneuver will serve a different purpose than the other TCMs. It is essentially an insurance policy for the orbiter. In case the trajectory is coming too close to Mars when it arrives, TCM-5 will be used to increase the altitude to what is needed for the Mars orbit insertion burn. The TCM-5 orbiter commands will be stored on-board the orbiter days before they are needed. The orbiter will have two burn opportunities - at 24 hours and at 12 hours before the MOI burn. During the last day before arrival, navigators will know if the orbiter coming too close. Mission managers can then choose to perform TCM-5. If the orbiter arrives at Mars on the expected trajectory, TCM-5 will never be needed.
Nothing yet...I suppose they are rather busy at JPL at the moment...
Posted by: Burmese Mar 3 2006, 07:06 PM
Regarding the possible conflict of communications channels between the rovers and MRO:
http://marsrovers.jpl.nasa.gov/mission/status.html
specifically:
"During the coming week, Spirit will communicate with Earth in UHF-only mode while NASA's Mars Reconnaissance Orbiter arrives at the red planet."
Posted by: Redstone Mar 3 2006, 08:10 PM
In the press conference, Jim Graf confirmed that both TCM 3 and TCM 4 were cancelled because of good navigational performance. I read that the team can calibrate the thrusters better than in the past, so that the TCM 1 and 2 were more accurate than in the past. Hence the later tweaking is not needed.
Posted by: djellison Mar 3 2006, 09:50 PM
If they get away without TCM5 ( the last minute job ) then it will have been a quite outstanding navigation solution - TCM2 was a peach
Doug
Posted by: Joffan Mar 6 2006, 01:06 AM
Posted by: The Messenger Mar 6 2006, 04:51 AM
Mars 2 was so close it did not need a final correction. There was not a contingency in the software for a burn of zero deration, and this is thought to have goofed up some of the bookkeeping & timing, screwing up the mission. I notice that on Cassini, when they cancel a burn, they quite often send modified code to replace what would have happened as part of the burn sequence.
Posted by: edstrick Mar 6 2006, 08:44 AM
I don't know if the real historical record is different from what was the "official" history 20 years+ ago, but supposedly Mars 2 had an attitude contol system failure and once it was in orbit, they had to spin-stabilize it in a slow rotation to keep it alive and all it returned of value was fields-and-particles data, and I don't think hardly anything was published from that, in comparision with Mars-3 orbiter data.
Posted by: yaohua2000 Mar 6 2006, 10:48 PM
Mars Reconnaissance Orbiter was only 1000000 kilometers away from Mars at 2006-03-06 21:22:47 UTC.
http://www.yaohua2000.org/cgi-bin/New%20Horizons.pl
Posted by: yaohua2000 Mar 8 2006, 10:29 PM
Mars Reconnaissance Orbiter was only 500000 kilometers away from Mars at 2006-03-08 22:14:28 UTC.
The velocity relative to Mars was 2.852 km/s. (13.9x slower than New Horizons relative to Pluto)
Posted by: volcanopele Mar 8 2006, 11:02 PM
here's an article from one of our local papers:
http://www.tucsoncitizen.com/news/local/030806a1_mars
Apparently, a version of the article posted earlier today described a Mars Renaissance Orbiter. Now a number of folks in the HiRise Operations Center (really just a tucked away hallway in our building) are dressed up in renaissance costumes...
Good grief, only a few more days until this madness ends.
Posted by: Bob Shaw Mar 8 2006, 11:39 PM
http://www.tucsoncitizen.com/news/local/030806a1_mars
Apparently, a version of the article posted earlier today described a Mars Renaissance Orbiter. Now a number of folks in the HiRise Operations Center (really just a tucked away hallway in our building) are dressed up in renaissance costumes...
Good grief, only a few more days until this madness ends.
Jason:
What better time to test the management's Equal Opportunities Policy than at a mission-critical moment?
Ah, the roar of the grease-paint! The smell of the crowd!
Men in what look like rather fetching little frocks...
Bob Shaw
Posted by: elakdawalla Mar 8 2006, 11:39 PM
Jason, that's something that just demands taking a photo that you can torture them with later
--Emily
Posted by: volcanopele Mar 8 2006, 11:54 PM
--Emily
Posted by: Tesheiner Mar 9 2006, 10:41 AM
This is the approx. timeline of MOI events:
10:24 a.m.: Final trajectory correction maneuver if needed
04:07 p.m.: Start spacecraft turn to orbit-insertion orientation
04:19 p.m.: Turn complete
04:24 p.m.: Orbit insertion rocket firing begins
04:45 p.m.: Spacecraft enters Martian shadow; on battery power
04:47 p.m.: Loss of signal as MRO passes behind Mars
04:51 p.m.: End of orbit insertion burn
05:13 p.m.: Spacecraft turns for Earth pointing
05:16 p.m.: Acquisition of signal
There was some discussion here before about the suspense until AOS and the two possible times --actually a range-- for that event, the earlier the worst.
My question is if there is really that "suspense" given that 23 of 27min of the firing will be made with MRO on sight i.e. with telemetry data? Off course, there are a lot of bad things that may happen on those later 4 minutes (or even later), but what would happen if the burn is cut short at exactly 23min? Would that be enough to enter orbit -- surely a very excentric one -- and would it be recoverable? If the answer is "yes" the suspense is really not that much, if the answer is "no" (knock on wood) there is actually no suspense, it's a bad day.
Posted by: djellison Mar 9 2006, 11:23 AM
Well - using Orbiter with a 400km MOI burn aim point - and this is all very rough
The trajectory switched from a flyby to an actual orbit after 26 mintues of Burn - so the bit of burn after LOS, is arguably the most critical
I think the time for reaquisition should be the big marker - I know they say it'll take half an hour of tracking to get a prelim. orbit for the spacecraft, but I'd have thought the actual time of reaquisition would probably be the giveaway as well.
Doug
Posted by: Sunspot Mar 9 2006, 11:47 AM
So a 26 minute engine burn is the minimum needed to enter into any kind of orbit? I remember them saying something simiilar during Cassini's arrival - about 73 minutes into the 96 minute engine burn
Posted by: djellison Mar 9 2006, 11:59 AM
I'm not sure of the exact figure - but the post MOI orbit is already very elliptical - I can imagine that it would only have to be a a little shy of the required Delta V to not make an orbit at all
Doug
Posted by: mcaplinger Mar 9 2006, 03:43 PM
The nominal burn is 26.8 minutes, of which 21.5 minutes are in view.
The minimum delta-V for capture is reached about 2 minutes after LOS.
Posted by: yaohua2000 Mar 10 2006, 03:40 AM
Mars Reconnaissance Orbiter was only 200000 kilometers away from Mars at 2006-03-10 03:18:30 UTC.
range-rate = -2.895 km/s
velocity = 2.897 km/s
Posted by: Rakhir Mar 10 2006, 08:02 AM
Watch Mars Reconnaissance Orbiter's Doppler Plot in real time during MOI !
http://marsprogram.jpl.nasa.gov/mro/mission/tl_doppler.html
Mars Orbit Insertion - Sequence of Events
http://marsprogram.jpl.nasa.gov/mro/mission/tl_moi-soe.html
Posted by: Borek Mar 10 2006, 08:20 AM
http://marsprogram.jpl.nasa.gov/mro/mission/tl_doppler.html
Mars Orbit Insertion - Sequence of Events
http://marsprogram.jpl.nasa.gov/mro/mission/tl_moi-soe.html
Why is the small version of the Doppler plot different from the large one?
And what is the discontinuity?
Borek
Posted by: mhall Mar 10 2006, 11:03 AM
I don't think the small one is live - at least, it hasn't changed in some minutes.
The discontinuity was labelled 'DSS 15 Handover' - I suppose this is when the DSN reception is being passed from one dish to the next.
Due to the rotation of the Earth, any given dish will have some additional velocity towards Mars as it (Mars) appears above the horizon; When Mars sets, the DSN dish is moving away from Mars at a similar velocity.
This means that the DSN station doppler is added to the MRO doppler; the DSN doppler is at its strongest, but in opposite directions, at handover.
Anyway, that's my take on it.
--Martin
Posted by: MERovingien Mar 10 2006, 11:52 AM
Hi everybody!
New to this board, although I have been lurking through these pages since the very beginning.
I have been bitting my nails on my own on MODY's MOI in 2001, then again for Spirit's and Oppy's arrival in 2004. So today, on MRO's MOI I have chosen to bite my nails in good company. In excellent company.
Go MRO!!
Posted by: The Messenger Mar 10 2006, 03:14 PM
http://marsprogram.jpl.nasa.gov/mro/mission/tl_doppler.html
Mars Orbit Insertion - Sequence of Events
http://marsprogram.jpl.nasa.gov/mro/mission/tl_moi-soe.html
Utterly cool.
We are seeing a sawtooth in the residuals @ ~6 minute intervals - is this due to attitude control, solution harmonics or what?
Posted by: jmknapp Mar 10 2006, 05:01 PM
We are seeing a sawtooth in the residuals @ ~6 minute intervals - is this due to attitude control, solution harmonics or what?
Interesting item from http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/8860/1/02-1411.pdf:
The resolution of the graph makes it hard to read, but it look like the amplitude of the sawtooth is a bit larger than with MRO (~5x), and the period about 15 minutes.
residuals such as that shown in Figure 5 exhibited a
peculiar sawtooth pattem. Because it appeared that we
were having problems fitting the data without the gasleak
acceleration estimation, we became concerned that
this may have been more evidence of serious problems
in the SIC modeling, the SDST, DSN hardware or the
ODP. Several DSN and NAG experts helped analyze
these unusual patterns, but no definitive explanation
was found. The DSN tracking procedures for Odyssey
had been to follow the S/C’s downlink frequency within
a fairly tight bandwidth by periodically ramping the
uplink signal. It was believed that this ramping of the
signal could have contributed to this problem,
especially if the values of the ramp rates were being
truncated, but no evidence of this was found. In the case
that this data was incorrect, our procedures were to
remove the data, however, it was determined that the
data had little effect on the OD solutions, especially due
to the signatures’ high fi-equency nature.
Posted by: Rakhir Mar 10 2006, 05:14 PM
There was a final TCM planned (if needed) at 15:24 UTC.
No change is visible on the doppler, so I guess it was cancelled (or too small to be seen).
-- Rakhir
Posted by: djellison Mar 10 2006, 05:16 PM
Press conf is on now - they did no TCM5
Doug
Posted by: The Messenger Mar 10 2006, 05:40 PM
The resolution of the graph makes it hard to read, but it look like the amplitude of the sawtooth is a bit larger than with MRO (~5x), and the period about 15 minutes.
Thanks - this is a good read, and the unmodel aspect - small forces corrections - required to hit the target make the cancelation of the finally 3-4 corrections very impressive navigation!
Oh, and the saw tooth? Still an unsolved mystery:)
Posted by: jmknapp Mar 10 2006, 05:55 PM
Comparing two NASA MRO prediction kernels, one for ideal MOI and one for no MOI, gives these predicted times (Earth-received UTC):
loss-of-signal: 21:46:09 MOI, 21:46:09 no-MOI (no difference)
aquisition-of-signal: 22:16:00 MOI, 22:08:56 no-MOI (no-MOI AOS being 7:04 earlier)
So when looking at the doppler plot, LOS should happen at 21:46:09 UTC regardless, and hopefully AOS will not be before 22:16:00 UTC. The time between 22:08:56 to 22:16:00 would be the critical time. I suppose that anything much after 22:16:00 would indicate too much of a burn.
Posted by: yaohua2000 Mar 10 2006, 06:14 PM
Mars Reconnaissance Orbiter was only 50000 kilometers away from Mars at 2006-03-10 17:25:55 UTC.
velocity = 3.111 km/s
range-rate = -3.082 km/s
Posted by: Nix Mar 10 2006, 06:57 PM
Hi guys, can I join the party?
-sitting on edge of seat for the coming hours as you all are I'm sure
Nico
Posted by: djellison Mar 10 2006, 07:10 PM
Feel free to join the rave
http://www.unmannedspaceflight.com/index.php?showtopic=2384&view=getnewpost
There's a big crowd..well.....3 of us
Doug
Posted by: mhall Mar 10 2006, 07:18 PM
Don't worry, we'll be watching when the time comes.
Posted by: Joffan Mar 10 2006, 07:24 PM
3 is a crowd, anyway.
So that's three TCMs all unneeded leading up to an orbit insertion burn. That is just an awesome performance, and if I were superstitious (which I'm not, touch wood) I would hope we haven't used up our luck early. 
Posted by: mhall Mar 10 2006, 07:27 PM
I presume that MRO's velocity is increasing as it approaches Mars, the doppler graph showing departure from the ideal Newtonian orbit.
The frequency of the sawtooth envelope seems to be increasing; perhaps it's related to velocity. Or something.
Posted by: yaohua2000 Mar 10 2006, 08:04 PM
Mars Reconnaissance Orbiter was only 20000 kilometers away from Mars at 2006-03-10 20:03:03 UTC.
velocity = 3.499 km/s
range-rate = -3.340 km/s
Posted by: yaohua2000 Mar 10 2006, 09:17 PM
Mars Reconnaissance Orbiter was only 5000 kilometers away from Mars at 2006-03-10 21:16:56 UTC.
velocity = 4.872 km/s
range-rate = -2.694 km/s
Posted by: imipak Mar 10 2006, 09:47 PM
*tumbleweed* bounces past as MRO reaches LoS & passes behind Mars with engines firing... my fingernails can't take this!
Posted by: ljk4-1 Mar 10 2006, 09:48 PM
MRO took a distant image of Deimos!
http://photojournal.jpl.nasa.gov/catalog/PIA02699
Original Caption Released with Image:
This image showing the position of the Martian moon Deimos against a background of stars is part of a successful technology demonstration completed by NASA's Mars Reconnaissance Orbiter before arrival at Mars.
The spacecraft's Optical Navigation Camera was used in February and March 2006 to demonstrate the use of pictures from a small camera for calculating precise location of a Mars-bound spacecraft by comparing the observed positions of Mars' two moons to their predicted positions relative to background stars. While this technique was not necessary for the Mars Reconnaissance Orbiter's own navigation, the demonstration prepares the way for relying on it for navigating precise arrivals for future missions that land on Mars.
This example image from the Optical Navigation Camera was taken on March 6, 2006, at a distance of 1.08 million kilometers (671,000 miles) from Deimos. That moon, the smaller of Mars' two, has a diameter of 15 kilometers (9 miles), and orbits 23,459 kilometers (14,577 miles) above the planet's surface.
Posted by: jaredGalen Mar 11 2006, 08:34 AM
I was reading the online profile on the nasa site of Tracy Drain who appeared on the Live coverage yesterday a bit.
http://www.nasa.gov/mission_pages/MRO/news/mrof-20060307.html
I came across this line and was quite surprised.
The content was up only in the past few days so I guess it was a bit rushed. Still amusing though.
Posted by: jabe Apr 20 2008, 09:50 PM
Here's a chart of the speed for the month of March:
hate reviewing a long dead thread..but...
I'm looking for the graphic that was posted in the post. Anyone have something similar? I'd like to use it as part of a lesson on space flight in my class when discussing the "sphere of influence".any help would be appreciated
cheers
jb
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