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Unmanned > Mars & Missions > Orbiters > Mars Odyssey
Doug M.
Long, informative press release from the Odyssey team today:;NewsID=1602

Key points: Odyssey has just yesterday made an orbital maneuver, which will cause its orbit to gradually evolve over the next 20 months. It's moving from an "evening" to a "morning" sun-synchronous orbit. The change is slow, and will be completed in November 2015. I thought this part of the article particularly interesting:

Odyssey flies in an orbit nearly over the poles and synchronized with the sun. For most of its first six years at Mars, the orbit was set at about 5 o'clock, local solar time. At every spot Odyssey flew over as it made its dozen daily passes from the north pole region to the south pole region, the local solar time was about 5 p.m. Beneath the south-to-north leg of the orbit, the time was about 5 a.m. That orbit provided an advantage for the orbiter's Gamma Ray Spectrometer to have its cooling equipment pointed away from the sun. The spectrometer checked for evidence of water near the Martian surface. It made important discoveries of how widely water ice -- detected as hydrogen-- and other elements are distributed on Mars.

Later, Odyssey worked for three years in a 4 o'clock orbit. That provided an advantage for mineral mapping by the orbiter's Thermal Emission Imaging System (THEMIS). Mid-afternoon warmth made minerals' infrared signatures easier to identify. This timing, however, added stress to Odyssey's power system. It put more of each orbit into the planet's shadow, where solar panels are unproductive. After providing radio-relay support for the 2012 landing of NASA's Curiosity Mars rover, a maneuver set Odyssey on a slow drift to later times of day to help preserve the spacecraft's aging battery.

THEMIS Principal Investigator Philip Christensen of Arizona State University in Tempe, proposed letting the time of the orbit shift past 6 o'clock and then making daylight observations on the south-to-north half of the orbit, at about 6:45 a.m., rather than the north-to-south half. The science team and NASA agreed, and the Odyssey project planned this week's maneuver to get to the desired orbit sooner.

"We don't know exactly what we're going to find when we get to an orbit where we see the morning just after sunrise," Christensen said. "We can look for seasonal differences. Are fogs more common in winter or spring? We will look systematically. We will observe clouds in visible light and check the temperature of the ground in infrared."

So, assuming the maneuver is successful, we could be looking at a whole new set of observations from Odyssey! Pretty amazing for a spacecraft that's already been in orbit for over twelve years.

One additional throwaway line caught my eye: right now they think they have enough propellant for 9 or 10 years. That's at the high end of earlier published estimates; presumably they've been able to refine their numbers. Very encouraging.

Doug M.
interesting, but this does rule out the use of MOdy for Opportunity, I think. It means that the orbiter flies above Meridiani either early in the morning, when Opportunity may not have enough solar or battery power to use its radio, or soon after sunset, when only battery power would be available.
That doesn't preclude using MODY for Opportunity whatsoever. The PM pass will just be a little later in the day (after which the rover can then deep-sleep)

The total amount of power generated by the arrays and the power consumed by doing a UHF pass don't change if you decide to do a UHF pass at 4pm or 6.30pm or 2pm. It's not like doing it later would require the heating of actuators etc.Turn it on. Use it. Turn it off. Same Whr comsumption be it 2pm, 4pm, 6pm, 4am...whatever.

The AM Odyssey passes ( typically 4am ) are only used when the rover has enough power to not do a deep-sleep. That will remain true if the AM pass is at 6.30am.

Apart from changing a few timings - I don't see any significant impact to Opportunity operations whatsoever.
Doug M.
I kicked the question back to the folks at Mars Outreach. Their answer: "Opportunity has a mechanism to modify its deep sleep start time to compensate for the change in Odyssey’s orbit. Also, the MRO spacecraft is also available to support Opportunity’s data relay needs in addition to those of Odyssey."

Doug M.
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