MRO MOI Events Timeline, Time Zone Friendly Options

[djellison]

Z = GMT / UT, P = Pacific
Future, Unconfirmed, Confirmed

NASA TV coverage starts at 2030Z / 1230P

TCM5 was not required.
2049Z / 1249P - Tank Pressurize - nominal pressure reported (@2053Z)
2103Z / 1303P - Switch to LGA ( 2 way doppler @ 2104Z, Lock at 160bps :2105Z)
2107Z / 1307P - Turn to Burn attitude (start of turn confirmed via doppler & telem @2110Z - Slew finished @2119Z via ACS)
2124Z / 1324P - Start of MOI Burn (confirmed via Doppler @2123Z )
(tank pressure about 3psi below predicts but within margins @2131Z )
(307m/sec accumulated delta @2135Z)
(401m/sec accumulated delta @2139Z)
(588m/sec accumualted delta @2144Z)
(telem. indicated eclipse entry @2146Z)
2146Z / 1346P - Loss of signal ( confirmed on doppler @2147Z- actual time 21:46:23Z)
2151Z / 1351P - Nominal End of Burn
2216Z / 1416P - Nominal AOS - (signal aquired - 1 way doppler @2116Z - 22:16:08 actual time)
(2 way doppler @2223Z)
2230Z / 1430p - 1641m/s burn indicated by telementry.

MRO is now orbiting the planet Mars

Status check at 2245Z
Flight Software - Burn done at 20% Utilisation
Prop Nominal
ACS, Earth point on reaction wheels, Star tracker aquisition ( 8 stars ), Burn time 1641 seconds vs 1606 expected. 1000.48 m/s compared to 1000.36m/s expected.
Thermal - all temps nominal. A few alarms due to soak back from the rcs thrusters.
EPS - Nomincal, trickle charging batts ( 110% state of charge ) - 870 Watts being used, 1650 Watts available from arrays.
Telecom - Nominal, on primary equipment, uplink and downlink signals as expected, already got a command in.
Fault Prot - Quicklook, no abnormal responses to the burn, out of go-fast mode.
Nominal termination to the MOI nominal block.






http://mars.jpl.nasa.gov/mro/realtime/mro-doppler_lg.html
Interesting Pre MOI PDF Presentation
http://www.hq.nasa.gov/office/codeq/smadir/hq06/landano.pdf



11th March 0030 Press Conf Update

Usual superlatives from senior management that don't tell us anything.

Jim Graff acknowledged help from NOAA w.r.t. Solar Weather, and the DSN's outstanding job.
Howard Eisan : MRO is safe, stable, on earth point, transmitting at 550kbps. We've earned the 'RO' of MRO. Dippled less than 10% into the batteries, commanded velocity change 2237.6 mph, overshot by 0.4mph, during the burn we underperformed by 2%, burned by 33 seconds longer to make up the difference. First hr of Nav data - orbit 35.5 hrs (predict 35.6) 264 x 28,000 mile orbit.
Rich Zurek : 2 of our 8 investigations were ones lost with MCO, one of those was also lost with Mars Observer. This completes replacement of all the Mars Observer instrumentation. We're going to knock your socks off - it's a good day.

Sally from TPS : Break for 2 weeks, what are you going to be doing (are you going to be celebrating for two weeks) - JG - stand down for w'end for a rest. Then prepare for aerobraking. ORT for Aerobraking, reconfig spacecraft for aerobraking, and some software patches to send up (9 uploaded to date, a few more to go). One other thing - we will take some early images - engineering images not science quality, make sure they work properly, processing that data on the ground to make sure the processing centres can extract the images from the data.

Sally asked when that science will start. RZ mentioned the use of aerobraking (lowest altitude is 60 miles) to understand structure of atmosphere. Sally asked if aerobraking is hard every orbit. RZ said that most of the closest approaches will be over the south pole. They dont expect big dust storms.

That's all the questions- again, kudos to Sally for asking them something. Unarguably the most important moment in Mars exploration since MER landing and potentially more important than anything between then and MSL landing scientifically, and in terms of infrastructure on orbit - $700M's worth of project - and that's three conferences where Sally was almost the only person to ask any questions. Either JPL PAO has furning the media with every single piece of information they could want before the event, or the media seem to be barely taking note of the mission because it's not as sexy as a landing ( there were plenty of spare seats in the V.K. auditorium, at Spirit's landing conf, you couldnt swing a cat in there ). Under-representation of mission rant over.

Doug

Attached File(s)

 doppler_1.mov ( 119.34K ) Number of downloads: 419

 

[Redstone]

From the press conference:

Contingency TCM-5 cancelled, as expected.
Good weather expected at DSN sites, so good communications expected.

Vehicle current mass is 4784 lbs, down 22 lbs from launch. 60lbs saved over the cruise which works out to 7 months operations at the end of the mission. Today 2/3 of the fuel will be consumed, about 1726 lbs.

Interestingly the 6 TCM engines fire along with the 6 main engines for most of the burn.

EDIT: some other notes:
MRO can underburn by 12% or overburn by 28% and still make Mars orbit. (I think I remember those numbers right.)
The fault protection system is not suppressed (like it was on Cassini), allowing the orbiter primary string to access all assets on the fully redundant string.
After Acquisition of Signal, ground will need about 5 minutes of telemetry to learn about the burn. 30 minutes of tracking to get an orbit solution.
MRO fault protection sequence, including shifting communication modes, takes 14 minutes. The ground will let it do so twice (so about half an hour) before taking any steps.

[yaohua2000]

From JPL Horizons, I prefer Orbiter UTC, so no Earth-received, no time zones, longitudes are areocentric:

2006-03-10 21:21:14, alt = 1000 km, lat = 73° S, lon = 285° E
2006-03-10 21:22:03, alt = 900 km, lat = 76° S, lon = 282° E
2006-03-10 21:22:57, alt = 800 km, lat = 80° S, lon = 278° E
2006-03-10 21:23:55, alt = 700 km, lat = 83° S, lon = 268° E
2006-03-10 21:25:02, alt = 600 km, lat = 86° S, lon = 232° E
2006-03-10 21:26:21, alt = 500 km, lat = 85° S, lon = 155° E
2006-03-10 21:28:09, alt = 400 km, lat = 78° S, lon = 130° E
2006-03-10 21:31:20, alt = 329 km, lat = 63° S, lon = 120° E

[mcaplinger]

Interesting Pre MOI PDF Presentation...

Interesting to say the least.

[djellison]

Google's a powerfull little sod sometimes.

Doug

[Redstone]

Coming up on pressurization...

And its confirmed!!

You could tell from the team reaction that this was a big deal. Sounds like there was a contingency plan, which has just been happily tossed in the bin.

Overheard ironic quote: "Well, that was easy!"

[Tom Tamlyn]

Overheard on NASA-TV: "That was easy!"

Coming up on pressurization...

And its confirmed!!

[Redstone]

All four pyros fired as expected. Pressurized on the main system.

[Redstone]

Slew to burn attitude has begun. It takes 12 minutes. Thats a sloooowww turn.

[Bjorn Jonsson]

Spacecraft performance nominal, all subsystems green...

[Marcel]

Spacecraft performance nominal, all subsystems green...

Burn, baby, burn !! Yeeehaaaah !!

[Redstone]

Here we go! All 6 engines up and running.

[ermar]

Aaaand it's gone! Half an hour to wait...

[um3k]

Now for the REALLY scary part...

[Marcel]

Can anyone tell me what's AOS.

[volcanopele]

AOS = Acquision of Signal

[tty]

Acquisition of signal

[Guest_AlexBlackwell_*]

Did I hear correctly? There was a 1% under- or overburn? Either is within the acceptable margin, though.

[yaohua2000]

Can anyone tell me what's AOS.

acquisition of signal

[RNeuhaus]

Hello, About the graph Mars Reconnaisence Orbiter Doppler, what is referring the y-axis (from 10,000 at the top and -90,000 at the bottom)?

Rodolfo

[Redstone]

Did I hear correctly? There was a 1% under- or overburn? Either is within the acceptable margin, though.

1 % underburn due to lower temperatures and hence lower pressures in the prop system, I think.

[djellison]

Did I hear correctly? There was a 1% under- or overburn? Either is within the acceptable margin, though.

Well - until AOS we're not going to know are we? The burn finished 'in the blind' from our perspsective. It might have been performing slightly under, but the spacecraft was counting delta-V, not seconds, so it should have just burnt 1% longer.

Doug

[tty]

Hello, About the graph Mars Reconnaisence Orbiter Doppler, what is referring the y-axis (from 10,000 at the top and -90,000 at the bottom)?

Rodolfo

Presumably Doppler shift in Hz.

[deglr6328]

mro website dead?

[Marcel]

Well - until AOS we're not going to know are we?
Doug

Will we know if it's OK AT the moment of signal appearance or does the orbit assesment needs to be done first to be sure ?

[RNeuhaus]

Only 5 minutes away to wait about the AOS millestone!

Rodolfo

New edit: plus about 13 minutes of lag time so it is 18 minutes later.

[Redstone]

Marcel, a signal means the spacecraft is healthy. They'll need 5 minutes of telemetry to get basic details on the burn. Need 30 minutes or so to get a fix on the resulting orbit.

[Nix]

We're ready MRO!

[paxdan]

NASA TV feed wow they look tense

[Bjorn Jonsson]

AOS !!!!!!!

[paxdan]

yay

[Nix]

One-way contact!

[tty]

AOS!

[deglr6328]

hushed yaaaaay! (still at work! )

[djellison]

GET IN

[paxdan]

"nice prop system dude!" "right on the money!"

[RNeuhaus]

Exit of Mars but we are going to know an official message by 5:30 pm EST (they knew it before than 5:30, at around 5:28 pm...watch out about the Control climate at NASA TV)

Rodolfo

A LITTLE STEP FOR GOOD NEWS : DSN has catched MRO

2219 GMT (5:19 p.m. EST)

Deep Space Network tracking stations in Madrid, Spain and Goldstone, California have locked on the spacecraft's signal. It will take a few minutes for enough data to be received from the spacecraft via the low-data rate to determine state of health and the orbit achieved.

Rodolfo

[Nix]

wooooooooooooooooooooooooooooooooooyay !!!!!!!!

Orbit! Congratulations!

[paxdan]

"we actually earned our 'O' today"

[Bjorn Jonsson]

2-Way Doppler, MRO is in orbit around Mars

[Rakhir]

4 orbiters and 2 landers operating at mars at the same time !
What a pleasant day !

-- Rakhir

[tty]

2-way Doppler

[um3k]

MRO is in orbit!

[Harder]

Orbit insertion OK

Doug, perhaps you need to insert a couple of terabytes of memory in this forum's server to accommodate the HIRISE extravaganza we can now expect.

Peter

[RNeuhaus]

2225 GMT (5:25 p.m. EST)

IN ORBIT! The Mars Reconnaissance Orbiter is truly an orbiter now after successfully swooping into orbit around the Red Planet today, mission control confirms!


WAW MRO IS ALREADY IN ORBIT

Rodolfo

[Marz]

2225 GMT (5:25 p.m. EST)

IN ORBIT! The Mars Reconnaissance Orbiter is truly an orbiter now after successfully swooping into orbit around the Red Planet today, mission control confirms!
WAW MRO IS ALREADY IN ORBIT

Rodolfo

Wahoo! I guess it's better to slightly underburn than overburn, since the aerobraking seems to have more variables to it, and it's always better to have more fuel than less fuel to correct the orbit. I'd imagine this won't add any extra time to the 6 month trim manuvers?

Time to celebrate another great day on mars! At this rate, JPL will need to add traffic control operations for mars.

[Joffan]

Time to celebrate another great day on mars! At this rate, JPL will need to add traffic control operations for mars.

mental image of 3 or 4 rovers jostling to take pictures of an interesting rock...

[MERovingien]

I can breathe again!

Congratulations to the JPL for another amazing mission!! 3 orbiters! 2 rovers!! Bravo!

[djellison]

Burn time 1641 seconds vs 1606 expected. 1000.48 m/s compared to 1000.36m/s expected.

So burn performance 97.87% of nominal, but actual Delta V 100.012% of predicted.

i.e. yes - the burn was a little under the mark, but the onboard sequence saw this, worked off the Delta V, and terminated the burn according to the accumulated Delta V hitting the right mark.

Doug

[lyford]

M-R-O-O-O-o-o-o-o!

[SFJCody]

Would be nice to have a Mars visualisation thingy that shows the locations of all four orbiters and two rovers.

[Marz]

Burn time 1641 seconds vs 1606 expected. 1000.48 m/s compared to 1000.36m/s expected.

So burn performance 97.87% of nominal, but actual Delta V 100.012% of predicted.

i.e. yes - the burn was a little under the mark, but the onboard sequence saw this, worked off the Delta V, and terminated the burn according to the accumulated Delta V hitting the right mark.

Doug

Excellent update! Thanks, Doug. I suppose this implies the aerobraking experienced less friction than anticipated, since the burn went longer than expected?

[djellison]

MOI and aerobraking are very seperate. The difference wasnt anything to do with aerobraking, I think it was simply a slight underperformance by the engines, and the sort of underperformance you only notice if you have a really long burn ( i.e. much bigger than TCM1 was).

First post in this thread updated with all the info from the 0030 conf.

We now have 6 spacecraft at work at Mars, that is a great thing.

Doug

[Redstone]

MRO isn't aerobraking yet. MOI took place outside the atmosphere (although Mars atmosphere does extend a long way, but very tenuously. The longer burn was due to the engines underperforming very slightly. Whether that was because of less thrust per unit of fuel or less fuel per unit of time is not clear yet.

EDIT: heh, knew someone would answer before me.

Zurek made a poignant point at the press conference, I thought. MRO has now completed the recovery of the loss of Mars Observer, whose instruments have been reflown on MGS, MCO (whose lost instruments have also been recovered), MODY and now MRO.

Space science teaches patience.

[Guest_Sunspot_*]

How many journalists attended the press conference lol ?. Hmmmm we really need to send someone from this forum to ask questions.

[RNeuhaus]

4 orbiters and 2 landers operating at mars at the same time !
What a pleasant day !

-- Rakhir

Maybe there are 6 orbiters including two Vikings are still looping on Mars, aren't they?

Rodolfo

Post-edit
Viking I is still orbiting around Mars at 320 x 56,000 km and it will crash on 2019.
Viking II is still orbiting around Mars at 302 x 33,176.
The other present orbiter is Mariner 9 until the year 2022.

[odave]

Sounds good to me - how would UMSF go about getting press credentials so we can dispatch "cub reporters" to various events? Much ado was made about the presence of bloggers at the political conventions during the 2004 US presidential campaign, and how this "Internet" thing was the wave of the future for journalism.

Anyhow, congratulations to all on the MRO team for a successful MOI. I can't wait for the images to start coming down!

[The Messenger]

From JPL Horizons, I prefer Orbiter UTC, so no Earth-received, no time zones, longitudes are areocentric:

2006-03-10 21:21:14, alt = 1000 km, lat = 73° S, lon = 285° E
2006-03-10 21:22:03, alt = 900 km, lat = 76° S, lon = 282° E
2006-03-10 21:22:57, alt = 800 km, lat = 80° S, lon = 278° E
2006-03-10 21:23:55, alt = 700 km, lat = 83° S, lon = 268° E
2006-03-10 21:25:02, alt = 600 km, lat = 86° S, lon = 232° E
2006-03-10 21:26:21, alt = 500 km, lat = 85° S, lon = 155° E
2006-03-10 21:28:09, alt = 400 km, lat = 78° S, lon = 130° E
2006-03-10 21:31:20, alt = 329 km, lat = 63° S, lon = 120° E

This was a braking manauver, the engine underperformed by 2%, but the approach was 71 km closer than the nominal target (400 km)? The delta V was returned to almost exactly nominal by burning longer, but I do not understand why this would result in a lower-than-expected altitude. (?) What am I missing this time?

[mcaplinger]

What am I missing this time?

1) The post you referenced was made before MOI even happened.
2) Horizons is using a trajectory that is weeks old.
3) I have no idea if "Orbiter" is propagating the elements from Horizons correctly anyway.

[Bob Shaw]

Maybe there are 6 orbiters including two Vikings are still looping on Mars, aren't they?

Rodolfo

Post-edit
Viking I is still orbiting around Mars at 320 x 56,000 km and it will crash on 2019.
Viking II is still orbiting around Mars at 302 x 33,176.
The other present orbiter is Mariner 9 until the year 2022.

Rodolfo:

There may be some Soviet vehicles still there, too. I doubt if they've all decayed so soon!

Bob Shaw

[Guest_BruceMoomaw_*]

I imagine the single biggest sigh of relief came from Dennis McCleese. He must feel like Charlie Brown after Lucy finally allowed him to kick the football.

[djellison]

Maybe there are 6 orbiters

But not 'operating' at mars.

Doug

[jmknapp]

One of the trajectory guys said on NASA TV yesterday that with the fuel they saved by not needing any course adjustments since last November they potentially extended the life of MRO by 9 months. They sure earned their pay (and maybe a bonus) for that accomplishment.

[deglr6328]

Burn time 1641 seconds vs 1606 expected. 1000.48 m/s compared to 1000.36m/s expected.

So burn performance 97.87% of nominal, but actual Delta V 100.012% of predicted.

i.e. yes - the burn was a little under the mark, but the onboard sequence saw this, worked off the Delta V, and terminated the burn according to the accumulated Delta V hitting the right mark.

Doug

This is really most fantastic. We are talking about a target change in velocity of over 2,200 mph and it was achieved to within a few inches per second!! that's some good engineering.

[RNeuhaus]

Rodolfo:

There may be some Soviet vehicles still there, too. I doubt if they've all decayed so soon!

Bob Shaw

All Soviet (not very sure, need more time to search about this to confirm), one Japan and all Mariner for Mars except one has flown by Mars and they are orbiting around the Sun. So now, there is 7 orbiting around Mars, three are inoperative (Vikings I, II and Mariner 9). In resume, up to know there is 65 % of MOI to Mars with success.

Rodolfo

[ljk4-1]

All Soviet (not very sure, need more time to search about this to confirm), one Japan and all Mariner for Mars except one has flown by Mars and they are orbiting around the Sun. So now, there is 7 orbiting around Mars, three are inoperative (Vikings I, II and Mariner 9). In resume, up to know there is 65 % of MOI to Mars with success.

Rodolfo

I know that Mariner 9 and the Vikings were placed in orbits around
Mars in part to stay up for at least 50 years to "remove" any micro-
organisms that might have survived on them.

The Soviet probes Mars 2, 3, and 5 were successful orbiters, but I
do not know if they are still in space or how well they were sterilized.

Phobos 2 did get into Mars orbit in 1989, but I read that it might
eventually crash into the moon it is named after. Anyone have an
orbital plot on this?

Mars 4 was supposed to orbit the Red Planet, but its braking rockets
failed. Mars 1, Zond 2, and Mars 6 and 7 were all flybys (the latter
two and possibly three with accompanying landers).

[Guest_AlexBlackwell_*]

I imagine the single biggest sigh of relief came from Dennis McCleese.

Who's that? Dan McCleese's son/nephew/uncle/grandfather?

[The Messenger]

Who's that? Dan McCleese's son/nephew/uncle/grandfather?

John Cleese's Irish cousin

The 2% lag in performance - Any clues as to why? TCM-2 was much more precise, or was there a performance correction during the burn as well?

[Circum]

The 2% lag in performance - Any clues as to why? TCM-2 was much more precise, or was there a performance correction during the burn as well?
[/quote]

During the NASA TV coverage, I believe I heard something about chamber pressures being slightly low, which was not a complete surprise since certain temperatures were also slightly low.

I didn't hear any explanation or further details about the low temperatures, but somehow I doubt it was 'new physics'. . . .

Also, could someone with more propulsion knowledge step in, I somehow have the impression that MOI was the first time they had pressurized the chamber, so did the TCMs use a different mode or different engines or something?

[djellison]

The engine's just didnt quite provide as much punch as they expected during MOI, so the onboard software commanded the shutdown slightly later than they expected it to happen.

If you're only doing a tiny nudge, a few m/sec - then it would be hard to notice a 2% shortfall in the expected performance ( I don't know if TCM 1 was done using a delta-V accumulation or a timer but either way, it'd be a tiny error on a small burn ) - whereas with a burn thats more than a thousand seconds then it's going to be a lot more obvious.

Doug

[ugordan]

Also, could someone with more propulsion knowledge step in, I somehow have the impression that MOI was the first time they had pressurized the chamber, so did the TCMs use a different mode or different engines or something?

I think this was the first and only time the propellant tanks were pressurized. The TCMs probably were run at default tank pressure, while before the MOI burn pyro-valves were opened to allow helium into the propellant tanks for pressurization. As Doug noted, the temperatures were slightly colder resulting in a somewhat lower prop tank pressure and, consequently, lower thrust.
The engines used on space probes are always pressure driven and the pressure of propellant tanks makes for quite a difference in thrust.
As a comparison, engines used on launch vehicles are turbopump driven and are vastly more complicated/expensive, but have the advantage of tanks not being required to handle great pressures (meaning they can be made light).

[mcaplinger]

did the TCMs use a different mode or different engines or something?

Yes. TCMs were done with the 22N thrusters alone, while MOI also used the 170N thrusters for the first time (press kit, page 36.)

[Circum]

Thanks for all the info dje, ugor, and mcap.

[Bob Shaw]

I know that Mariner 9 and the Vikings were placed in orbits around
Mars in part to stay up for at least 50 years to "remove" any micro-
organisms that might have survived on them.

The Soviet probes Mars 2, 3, and 5 were successful orbiters, but I
do not know if they are still in space or how well they were sterilized.

Phobos 2 did get into Mars orbit in 1989, but I read that it might
eventually crash into the moon it is named after. Anyone have an
orbital plot on this?

Mars 4 was supposed to orbit the Red Planet, but its braking rockets
failed. Mars 1, Zond 2, and Mars 6 and 7 were all flybys (the latter
two and possibly three with accompanying landers).

Yes; I think Rodolfo has missed the four Soviet vehicles placed in orbit around Mars, though whether they still are is another issue.

Bob Shaw

[ToSeek]

Yes. TCMs were done with the 22N thrusters alone, while MOI also used the 170N thrusters for the first time (press kit, page 36.)

That's not quite true. TCM 1 was used to check out the main engines. See this press release.

[The Messenger]

The 2% lag in performance - Any clues as to why? TCM-2 was much more precise, or was there a performance correction during the burn as well?
During the NASA TV coverage, I believe I heard something about chamber pressures being slightly low, which was not a complete surprise since certain temperatures were also slightly low.

I didn't hear any explanation or further details about the low temperatures, but somehow I doubt it was 'new physics'. . . .

New physics would not seem to be necessary...but they cannot be eliminated, either

Another aside, there have been new developments in hydrogen containment vessels compatible with the grueling temperature swings of solar space. Espect to see these leak-proof containers, and more dependance upon hydrogen fuels and propulsion systems in interplanetary space flight in the future.

[RNeuhaus]

Yes; I think Rodolfo has missed the four Soviet vehicles placed in orbit around Mars, though whether they still are is another issue.

Bob Shaw

Thanks to ljk4-1 and Bob. I have already checked about the Soviet's Mars program. Only four Russian cosmos probes are orbiting on Mars: Mars 2, 3, 5 and 6. 4 and 7 have missed and are on the solar orbit.

Rodolfo

[Guest_BruceMoomaw_*]

No, Mars 6 isn't orbiting Mars (and never did; it was a flyby that dropped off a lander). But Phobos 2 IS orbiting Mars (unless it's run into Phobos -- as suggested above -- which seems unlikely to me).

[edstrick]

Mars 2 was in a very very eccentric -- was it 19 days long? -- orbit. It would have been strongly pushed around by tidal effects and plausibly has hit the atmosphere by now.

[tedstryk]

Mars 2 was in a very very eccentric -- was it 19 days long? -- orbit. It would have been strongly pushed around by tidal effects and plausibly has hit the atmosphere by now.

Actually, that was Mars 3. Mars 2 was in a short orbit, but had transmitter problems. And Mars 5 may still be in orbit.

[edstrick]

Yep.. you're right.

[Bubbinski]

Would be nice to have a Mars visualisation thingy that shows the locations of all four orbiters and two rovers.

I wonder if the latest Starry Night software fills this bill, it is advertised as tracking spaceprobes. That would be very nice to have.

[helvick]

I wonder if the latest Starry Night software fills this bill, it is advertised as tracking spaceprobes. That would be very nice to have.

Celestia will do it but you'll have to search the forumsfor some add-ons to get all the current orbiters models and orbits.

[mcaplinger]

Celestia will do it but you'll have to search the forumsfor some add-ons to get all the current orbiters models and orbits.

The thread at http://www.unmannedspaceflight.com/index.php?showtopic=2367 goes into a tedious level of detail as to why Celestia orbital elements probably won't be correct for orbiters in low sun-sync orbits. The same is true for Starry Night. There's some hope that Celestia SampledOrbits can be defined that will be right over the time they cover, but there's still work left to do on that.

[Decepticon]

Does JPL take this stray probes into account when putting new probes into orbit?

Or is the risk factor to small to even worry?

[Guest_BruceMoomaw_*]

MUCH too small to worry about. Even in the environment of low Earth orbit -- which is now getting frighteningly crowded -- there have been only 2 or 3 significant collisions with small bits of junk (and a lot of those have been scattered by bursting rocket upper stages, or are drops of solidified metallic coolant from the leaky nuclear reactors on the old Soviet recon satellites -- two things we don't have to worry about in Mars orbit).

[mcaplinger]

Does JPL take this stray probes into account when putting new probes into orbit?

Part of the MRO MOI viewgraph package was a COLA (Collision Avoidance) analysis for Phobos, Deimos, and the currently operating orbiters. We don't really know where the dead ones are, so there is no sensible analysis that can be performed. As Bruce said, the probabilities are low, but for bodies with known ephemerides, the analysis is pretty easy, so it might as well be done.

[Gsnorgathon]

Any chance that MARSIS or SHARAD could be used to locate them?

[Bubbinski]

Isn't Marsis the Mars Express ground pointing radar? Interesting thought....even though the risk is low it would still be a great idea to try to track dead probes and scan the space around Mars. But I wonder how this could be done, do we even have radars on earth powerful enough (Arecibo?) to scan Martian orbital space?

More and more spacecraft will hopefully make it to Mars in the near future....it might be prudent now to start on a more extensive COLA/tracking/space debris reduction program before it becomes an issue. Same with the Moon.

[mcaplinger]

Any chance that MARSIS or SHARAD could be used to locate them?

MARSIS uses wavelengths between 50 and 230 meters; SHARAD around 15 meters. I doubt either could detect an object as small as a spacecraft.

[Bob Shaw]

More and more spacecraft will hopefully make it to Mars in the near future....it might be prudent now to start on a more extensive COLA/tracking/space debris reduction program before it becomes an issue. Same with the Moon.

Lunar orbits tend to be quite unstable, especially low ones, so there's almost certainly nothing other than SMART-1 in Lunar orbit at present - we're a long way from needing traffic cops there!

Bob Shaw

[Guest_BruceMoomaw_*]

An odd note from the March 6 Aviation Week: The pre-MOI repressurization of the hydrazine tank "caused a little anxiety because Mars Observer was lost at the same point in 1993, believed due to overpressurized tanks from a faulty orifice in the pressure regulator sensing line."

This is a totally different theory for Mars Observer's loss from the one I've always seen listed as most probable: nitrogen tetroxide oxidizer leaking past a check valve into the hydrazine lines and setting off an explosion in the latter when the hydrazine first came down them. Is AW mistaken and the pressure-regulator theory is just one of the less likely alternate possible causes listed in the MO failure report, or has there been some recent rethinking on the most probable cause of the accident?

[edstrick]

I was looking at that report and wondering the exact same thing....

I suspect a lot of the engineers and reporters have never read or essentially forgotten the full range of plausible failure modes ... I sure have forgotten all but the "somewhat most plausible" one.... and the reporter may be quoting one engineer or manager's take on the MO failure who's also working from memory.

[Jim from NSF.com]

Maybe this was the only plausible failure mode applicable to MRO

[edstrick]

Engineers and mission controllers on these missions have incredible regenerative abilities .... they routinely chew their fingernails back to their armpits during the runup to these mission critical events.

[mcaplinger]

Is AW mistaken and the pressure-regulator theory is just one of the less likely alternate possible causes listed in the MO failure report, or has there been some recent rethinking on the most probable cause of the accident?

The latter. From "Propulsion Lessons Learned from the Loss of Mars Observer", Carl S.Guernsey, JPL, 2001:
"This paper presents an overview of the potential failure modes identified by the JPL review board and presents evidence, discovered after the failure reviews were complete, that the loss was very likely due to the use of an incompatible braze material in the flow restriction orifice of the pressure regulator."

Complete paper is online at
http://www.klabs.org/richcontent/Reports/F...y_a01-34322.pdf

[Guest_BruceMoomaw_*]

Ah! This is a big item that's totally new to me. Thanks.

[tuvas]

An odd note from the March 6 Aviation Week: The pre-MOI repressurization of the hydrazine tank "caused a little anxiety because Mars Observer was lost at the same point in 1993, believed due to overpressurized tanks from a faulty orifice in the pressure regulator sensing line."

This is a totally different theory for Mars Observer's loss from the one I've always seen listed as most probable: nitrogen tetroxide oxidizer leaking past a check valve into the hydrazine lines and setting off an explosion in the latter when the hydrazine first came down them. Is AW mistaken and the pressure-regulator theory is just one of the less likely alternate possible causes listed in the MO failure report, or has there been some recent rethinking on the most probable cause of the accident?

If I remember right, the pressurization was such a big deal because there was a fairly last-minute change in the code, as I recall, it was set up so there wasn't a redundancy previous to a reprogramming only a few weeks before MOI. I attended a MOI party at the University of Arizona with the HiRISE team (This was right before I joined, my hiring was contitional upon the safe MOI of MRO, imagine that!), and I think that was the story that I heard at the UA MOI party... But, it's been quite a while... Also, please note that I wasn't a HiRISE team member at this point in time, so I don't know if that's really the reason. If that was the reason, then it just goes to show that NASA isn't taking any more chances with it's spacecraft, they are constantly checking things to make them better. MRO has performed almost flawlessly, even with it's more complex than normal instruments.