Mro On Approach, TCM-3 not required Options

[Redstone]

MRO has shifted from the cruise phase to Approach phase. 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!

[RNeuhaus]

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/cruis...oach_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

[ugordan]

I seems that MRO has started to gain its speed due to Mars gravity tug, has not?

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.

[abalone]

MRO has shifted from the cruise phase to Approach phase. 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!

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??

[djellison]

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

[SFJCody]

How many pixels would HiRise get across the disc of Mars now?

[mcaplinger]

How many pixels would HiRise get across the disc of Mars now?

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.

[djellison]

This is from a little PDF I found at the same place as the UHF tracking info

Attached thumbnail(s)

 

[crabbsaline]

This is from a little PDF I found at the same place as the UHF tracking info

Thanks Doug. I had to look up ONC 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.

[djellison]

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

[jmknapp]

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.

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:

[jmknapp]

PS: Does anyone know what the field-of-view and resolution of the ONC are?

[djellison]

http://bookstore.spie.org/index.cfm?fuseac...d=619857&coden=

Abstract
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.

[jmknapp]

http://bookstore.spie.org/index.cfm?fuseac...d=619857&coden=
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.

[Bob Shaw]

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