NASA's Mars Reconnaissance Craft Begins Adjusting Orbit
NASA/Jet Propulsion Laboratory
March 31, 2006
Full Version: MRO aerobraking campaign
Article with first Mars Climate Sounder images:
http://www.spaceref.com/news/viewsr.html?pid=20143
See also:
http://www.nasa.gov/mission_pages/MRO/news/mro-20060331.html
Bob Shaw
http://www.spaceref.com/news/viewsr.html?pid=20143
See also:
http://www.nasa.gov/mission_pages/MRO/news/mro-20060331.html
Bob Shaw
QUOTE (Bob Shaw @ Apr 3 2006, 12:58 AM) 
Article with first Mars Climate Sounder images:
http://www.spaceref.com/news/viewsr.html?pid=20143
http://www.spaceref.com/news/viewsr.html?pid=20143
What's with that jaggedness in the second and third image? It's as though 2 frames were incorrectly aligned?
I think the instrument scans in 'stripes' - and it looks as if there are three stripes in that image. Due to motion of the spacecraft I suppose, the three stripes don't quite line up properly. The MCS website is at TPS, might be worth emailing them and asking about it.
Doug
Doug
The release says the images were taken from a distance of around 45 000 km. That's about periapsis so Mars-spacecraft distance change should have been negligible. It does look to me like a case of bad mosaicking more than spacecraft motion. Perhaps this was just a quick-and-dirty release to see whether the instrument works correctly, but even then how hard could it be to manually align the strips?
EDIT: They say the instrument indeed scans across the disc so without precise, reconstructed spacecraft attitude pointing knowledge this is probably the best they can do at the moment.
EDIT: They say the instrument indeed scans across the disc so without precise, reconstructed spacecraft attitude pointing knowledge this is probably the best they can do at the moment.
It certainly isn't anything to worry about.
QUOTE (BruceMoomaw @ Apr 3 2006, 01:31 PM)
It certainly isn't anything to worry about.
Nobody said that. But it certainly is an aesthetic issue.
QUOTE (djellison @ Apr 3 2006, 01:48 AM)
I think the instrument scans in 'stripes' - and it looks as if there are three stripes in that image. Due to motion of the spacecraft I suppose, the three stripes don't quite line up properly. The MCS website is at TPS, might be worth emailing them and asking about it.
That's one of the questions I have for the team, but I haven't managed to get a conversation in with any of them yet. They seem to be a little busy. The instrument is a linear array, so it does need to be scanned to gather a 2D image. Another possibility comes to mind: perhaps they scanned part of the planet, but had to slew off to do a calibration (they have 2 internal cal targets and also calibrate on dark sky) in the middle of the observation? Anyway, I'll ask.
--Emily
they are indeed multiple scans.
might be due to the spacecraft coming closer or due to slew rates being different between the scans. My guesses anyway.
might be due to the spacecraft coming closer or due to slew rates being different between the scans. My guesses anyway.
I would assume the jaggies are the results of quick-look processing of data under non-standard conditions.
What *IS* important is that it shows high data quality and low noise, even in the low-signal 15 micron upper-atmosphere channel. That data is on of probably several in the 15 micrometer CO2 absorption band. It actually runs from 13 or 14 microns to 16 or 17. Atmospheric opacity increases from the edges to the center of the band and narrow wavelength bands across this spectral feature probe to different depths in the atmosphere before the CO2 becomes opaque.
Mariner 9 first used it for atmosphere temperature profiling. Viking Orbiters' IRTM (infrared thermal mapper) had a single detector in the middle of the channel for crude stratospheric temperature observations. Global Surveyor's TES gets atmosphere profiles in the band the same way Mariner 9 did. Limb scanning with narrow slits at wavelengths in and on the flanks of this band will yield high precision, high resolution vertical temperature profiles day and night.
What *IS* important is that it shows high data quality and low noise, even in the low-signal 15 micron upper-atmosphere channel. That data is on of probably several in the 15 micrometer CO2 absorption band. It actually runs from 13 or 14 microns to 16 or 17. Atmospheric opacity increases from the edges to the center of the band and narrow wavelength bands across this spectral feature probe to different depths in the atmosphere before the CO2 becomes opaque.
Mariner 9 first used it for atmosphere temperature profiling. Viking Orbiters' IRTM (infrared thermal mapper) had a single detector in the middle of the channel for crude stratospheric temperature observations. Global Surveyor's TES gets atmosphere profiles in the band the same way Mariner 9 did. Limb scanning with narrow slits at wavelengths in and on the flanks of this band will yield high precision, high resolution vertical temperature profiles day and night.
On last wednesday, MRO has started to swoop down to very close to Mars' atmosphere (between 107-112 km from surface) and will continue many passes over the next 6 months.
On Wednesday, a short burn of intermediate sized thrusters while the orbiter was at the most distant point nudged the spacecraft to pass from approximately 70 miles (112 kilometers) to within 66 miles (107 kilometers) of Mars' surface.
Details from Universe Today Web : Mars Reconnaissance Orbiter Adjusts its Orbit
Hence, MRO will have a heating stuff every passing time.
Rodolfo
On Wednesday, a short burn of intermediate sized thrusters while the orbiter was at the most distant point nudged the spacecraft to pass from approximately 70 miles (112 kilometers) to within 66 miles (107 kilometers) of Mars' surface.
Details from Universe Today Web : Mars Reconnaissance Orbiter Adjusts its Orbit
Hence, MRO will have a heating stuff every passing time.
Rodolfo
MRO aerobraking progress from an article from space.com
“The spacecraft is presently well on its way through its aerobraking phase having completed approximately five out of 24 weeks of activity—or around 20 percent—relative to the calendar,”
Here is the link to full article :
http://www.space.com/missionlaunches/060512_mro_braking.html
“The spacecraft is presently well on its way through its aerobraking phase having completed approximately five out of 24 weeks of activity—or around 20 percent—relative to the calendar,”
Here is the link to full article :
http://www.space.com/missionlaunches/060512_mro_braking.html
New Space.com article on MRO - now in a 20 hour orbit
When the spacecraft first entered orbit around Mars, its farthest point from the planet was about 45,000 kilometers (28,000 miles). After 11 weeks of aerobraking operations, this distance has been reduced to about 20,000 kilometers (12,000 miles).
On each orbit since early April, the nearest-to-Mars portion of the orbit has passed through the upper atmosphere, usually at about 105 kilometers (65 miles) above the surface of the planet. The drag created by interaction of the atmosphere with spacecraft surfaces slows the craft.
There is still 12-week process of shrinking its orbit.
"We've finished about 80 of them so far, but we have about 400 more to go, and the pace really quickens toward the end," he added.
http://www.marsdaily.com/reports/Pace_Quic...rs_Orbiter.html
Rodolfo
On each orbit since early April, the nearest-to-Mars portion of the orbit has passed through the upper atmosphere, usually at about 105 kilometers (65 miles) above the surface of the planet. The drag created by interaction of the atmosphere with spacecraft surfaces slows the craft.
There is still 12-week process of shrinking its orbit.
"We've finished about 80 of them so far, but we have about 400 more to go, and the pace really quickens toward the end," he added.
http://www.marsdaily.com/reports/Pace_Quic...rs_Orbiter.html
Rodolfo
Is there any source of info showing how the orbit of MRO is changing (Periapsis changes, altitude of pass). NASA did this for MGS in real time during aerobraking. There was also near realtime transponder data for the radios, cameras, motors etc. They are not reporting as exhaustively or frequently for MRO, at least at this early stage. Will this improve?
QUOTE (MarkL @ Jul 17 2006, 03:26 PM)
Is there any source of info showing how the orbit of MRO is changing (Periapsis changes, altitude of pass). NASA did this for MGS in real time during aerobraking. There was also near realtime transponder data for the radios, cameras, motors etc. They are not reporting as exhaustively or frequently for MRO, at least at this early stage. Will this improve?
Most of these web-based bells 'n' whistles-type features are PR-driven, so if that feature isn't available for MRO, I suspect there hasn't been much demand for it. Remember that with MGS, aerobraking was a relative novelty, Magellan notwithstanding, and there wasn't a whole lot else going at Mars at the time.
I've been able to follow MRO's arobraking process here graphically..no idea how accurate it is though but neat thing is MRO's orbit can be totally seen now..it used to be cut off since ellispe was too big for display..or so I think. At least this way I feel like somthing is happening rather than waiting for infrequent updates..
cheers
jb
but neat thing is MRO's orbit can be totally seen now..it used to be cut off since ellispe was too big for display..or so I think. At least this way I feel like somthing is happening rather than waiting for infrequent updates..cheers
jb
The last reported news from MRO was on May 10 which says
"NASA's latest orbiter to visit the Red Planet is well into its main phase of aerobraking. Mars Reconnaissance Orbiter has cut about 10 hours off of its initial orbit by strategically dipping in and out of Mars' thin atmosphere.
Now at a 25 hour-orbit, the spacecraft is circling the planet roughly once per martian sol (day), which is 24 hours, 39 minutes."
Let us suppose that MRO's aerobraking calendar is in the fifth month of 8 months middle since March 10 and it is going to finish soon, by the beginning of November 2006 according to the Mission MR0's calender.
Is the MRO's above calendar on the time? Hope that MRO's has a new update status report soon.
Rodolfo
"NASA's latest orbiter to visit the Red Planet is well into its main phase of aerobraking. Mars Reconnaissance Orbiter has cut about 10 hours off of its initial orbit by strategically dipping in and out of Mars' thin atmosphere.
Now at a 25 hour-orbit, the spacecraft is circling the planet roughly once per martian sol (day), which is 24 hours, 39 minutes."
Let us suppose that MRO's aerobraking calendar is in the fifth month of 8 months middle since March 10 and it is going to finish soon, by the beginning of November 2006 according to the Mission MR0's calender.
Is the MRO's above calendar on the time? Hope that MRO's has a new update status report soon.
Rodolfo
Typically - they end up a little bit ahead of the aerobraking time line - (they plan conservatively) - but the plan I believe is to get the aerobraking done before solar conjunction - and then start science AFTER solar conjunction.
Doug
Doug
They are in an orbit with the inclination set by the end of the periapsis lowering burns shortly after orbit insertion. The initial orbit is relatively fixed in inertial space and as Mars moves in orbit around the sun, the day/night geometry moves under the orbit.
However, as the orbit gets more and more circular, the orbit precesses more and more under the influence of the oblate (bulging at the equator due to Mars' rotation) gravity field of the planet. Once they are in circular orbit, the orbit will precess exactly 360 degrees (one full rotation) per martian year. Except for the effect of Mars speeding up and slowing down in it's elliptical orbit arouind the sun, the equator crossing times of the precessing circular orbit will be fixed at the same time of day.
The equator crossing times are carefully picked for the overall "best" science from all instruments: good illumination for spectrometers, good shadows for imaging, etc. So they are timing the arrival in circular orbit to coincide with the orbit having rotated to the optimum equator crossing time.
However, as the orbit gets more and more circular, the orbit precesses more and more under the influence of the oblate (bulging at the equator due to Mars' rotation) gravity field of the planet. Once they are in circular orbit, the orbit will precess exactly 360 degrees (one full rotation) per martian year. Except for the effect of Mars speeding up and slowing down in it's elliptical orbit arouind the sun, the equator crossing times of the precessing circular orbit will be fixed at the same time of day.
The equator crossing times are carefully picked for the overall "best" science from all instruments: good illumination for spectrometers, good shadows for imaging, etc. So they are timing the arrival in circular orbit to coincide with the orbit having rotated to the optimum equator crossing time.
Has anyone new information about the Ka-Band transmitter problem / failure(?) during aerobreaking?. If this can't be fixed, the planned mission can be done using X-band (as baselined), but the higher downlink rate with Ka-Band would not be possible (supplementing X-band planned after Ka-band engineering testing).
Analyst
Analyst
'more' information - I've not heard ANY information suggesting that the Ka band has stopped working.
Doug
Doug
QUOTE (Analyst @ Aug 1 2006, 06:50 AM)
Has anyone new information about the Ka-Band transmitter problem / failure(?) during aerobreaking?. If this can't be fixed, the planned mission can be done using X-band (as baselined), but the higher downlink rate with Ka-Band would not be possible (supplementing X-band planned after Ka-band engineering testing).
All the mission planning is based on X-band data rates. Ka-band is a true experiment
Sure, Ka-band is an experiment and the baseline is X-band. BUT Ka-band, if it works, could increase the downlink volume above the planned volume. This would be useful. He said, thinking about the high resolution camera.
Analyst
Analyst
QUOTE (Analyst @ Aug 1 2006, 01:51 PM)
Sure, Ka-band is an experiment...
Analyst
Analyst
But what's wrong with it???
B)-->
But what's wrong with it???
[/quote]
There are 6 science instruments and 3 payloads for technology objectives (Electra, Optical Navigation Camera and Ka-band) on MRO, reference: Press Kit.
The Ka-band experiment is not needed for the MRO science mission, e.g. the data return from the 6 science instruments and radio science. All the planned science data can be transmitted via X-band. Ka-band is primarely only a test for future spacecraft. But it could be used, after these testings, for science data transmission at higher data rates than possible with X-band. Thus more science data, thus more pictures. This was (is) anticipated. If there are problems with the Ka-band transmitter, or in a worst case scenario it failed, you can't do the testing. This does not influence your planned science mission, but you can't get a higher Ka-band data rate. Compare this with MER: planned duration 90 sols, mission success; longer duration is a bonus. Without Ka-band you lose the bonus.
I don't know what's wrong with Ka-band. I only know something has been. And I don't know if it is an issue any more or not. That's been my question in the first place.
Analyst
QUOTE(Toma B @ Aug 1 2006, 12:38 PM)
But what's wrong with it???
[/quote]
There are 6 science instruments and 3 payloads for technology objectives (Electra, Optical Navigation Camera and Ka-band) on MRO, reference: Press Kit.
The Ka-band experiment is not needed for the MRO science mission, e.g. the data return from the 6 science instruments and radio science. All the planned science data can be transmitted via X-band. Ka-band is primarely only a test for future spacecraft. But it could be used, after these testings, for science data transmission at higher data rates than possible with X-band. Thus more science data, thus more pictures. This was (is) anticipated. If there are problems with the Ka-band transmitter, or in a worst case scenario it failed, you can't do the testing. This does not influence your planned science mission, but you can't get a higher Ka-band data rate. Compare this with MER: planned duration 90 sols, mission success; longer duration is a bonus. Without Ka-band you lose the bonus.
I don't know what's wrong with Ka-band. I only know something has been. And I don't know if it is an issue any more or not. That's been my question in the first place.
Analyst
QUOTE (Analyst @ Aug 1 2006, 03:05 PM)
I only know something has been.
What?
Doug
Besides the very fact of a problem (Ka-band not working) I don't know what has been wrong nor do I know if it is still wrong.
If this sounds like I don't know much, this exactly is the reason because I ask.
Analyst
If this sounds like I don't know much, this exactly is the reason because I ask.
Analyst
QUOTE (Analyst @ Aug 1 2006, 07:25 AM)
Besides the very fact of a problem (Ka-band not working) I don't know what has been wrong nor do I know if it is still wrong.
If this sounds like I don't know much, this exactly is the reason because I ask.
Analyst
If this sounds like I don't know much, this exactly is the reason because I ask.
Analyst
Could you point us to a location where you got the information about something wrong with Ka-Band or who you heard it from? Like Doug posted earlier I haven't heard/seen or found anything, not even a peep.
Part in a pre-amp failed
Sad. Does this mean Ka-band is gone forever or is there an alternative / workaround?
Analyst
Analyst
QUOTE (Jim from NSF.com @ Aug 3 2006, 12:21 AM)
Part in a pre-amp failed
Still no reference!?
QUOTE (centsworth_II @ Aug 3 2006, 03:23 PM)
Still no reference!?
Jim from NSF.com
Joined: 6-April 06
From: Cape Canaveral
Member No.: 734
and to quote Jim's signature type thing at NSF.com "Actually, I am a rocket scientist."
If I'm wrong fair enough and I got people mixed up, otherwise I believe it
QUOTE (Analyst @ Aug 3 2006, 02:11 AM)
Sad. Does this mean Ka-band is gone forever or is there an alternative / workaround?
Analyst
Analyst
It was an experiment and not required for the primary mission. No work around
QUOTE (Jim from NSF.com @ Aug 3 2006, 07:52 PM)
It was an experiment and not required for the primary mission. No work around
Was it two way or one way? "part in a pre-amp" sounds like something in the receive path. Maybe they could at least test the other half?
From the MRO Press Kit:
The amplifiers are needed for the downlink path, and there is definitely only one for Ka-band and therefore very likely only one pre-amplifier for Ka-band. I am pretty sure there is no Ka-band recieve path.
Analyst
QUOTE
To communicate with Earth, the spacecraft has three antennas, three amplifiers and two transponders.
[...]
Two of the three amplifiers boost signals in the X-band of radio frequencies, planned as the primary channel for the mission. One of these is a backup in case the first fails. Each can send signals at 100 watts of power. The third amplifier supports the mission's demonstration of using the shorter-wavelength Ka band as an alternate channel. It can send signals at 35 watts.
[...]
Two of the three amplifiers boost signals in the X-band of radio frequencies, planned as the primary channel for the mission. One of these is a backup in case the first fails. Each can send signals at 100 watts of power. The third amplifier supports the mission's demonstration of using the shorter-wavelength Ka band as an alternate channel. It can send signals at 35 watts.
The amplifiers are needed for the downlink path, and there is definitely only one for Ka-band and therefore very likely only one pre-amplifier for Ka-band. I am pretty sure there is no Ka-band recieve path.
Analyst
http://trs-new.jpl.nasa.gov/dspace/handle/2014/7087
I've not seen any anticipated Ka band data rates, but it features in the MRO scheduling only as an experiment from time to time, so its loss is not going to negatively effect the return.
Doug
I've not seen any anticipated Ka band data rates, but it features in the MRO scheduling only as an experiment from time to time, so its loss is not going to negatively effect the return.
Doug
No doubt it is an (now failed) experiment, but the same can be said for the HST NICMOS cryocooler installed during STS-109. It is not needed for mission success, but is nice to have it. And it effects the potential return.
The MRO Press Kit says:
Analyst
The MRO Press Kit says:
QUOTE
The mission will use X-band radio frequencies as its principal communication channel with Earth. Counting the capacity from supplemental use of 70-meter antennas as well as two daily sessions with 34-meter ones, the quantity of data received per day via X band is expected to vary from about 40 to 90 gigabits (about 60 to 140 CD-ROMs worth). The mission will also demonstrate the use of Ka band radio frequencies. After that demonstration's goals are met, Ka band transmissions might add significantly to the total amount of science data sent to Earth by the orbiter. The Ka band equipment uses less power than its X band counterpart to send the same amount of data. However, Ka band transmissions are more susceptible to being disrupted by water in Earth's atmosphere.
Analyst
QUOTE (hendric @ Aug 4 2006, 04:08 AM)
Was it two way or one way? "part in a pre-amp" sounds like something in the receive path. Maybe they could at least test the other half?
Science downlinks are separate from command uplinks. Not the same systems
Didn't hear anything about the Ka-band band till now..that really sucks..ah well one more reason to send another big orbiter to Mars
Looking at MRO's present orbit , if the graphics are to be believed, the orbit is under 4 hours... since the orbit is so short the orbits seems to be shrinking quite fast..I'm just hoping it does represent the real position..not a guessed one and we find out MRO is really in a 8 hour orbit
Can't wait for the first pics to come down.. hope they pass over some of the "lost" landers and try to take pics sooner rather than later..
cheers
jb
Looking at MRO's present orbit , if the graphics are to be believed, the orbit is under 4 hours... since the orbit is so short the orbits seems to be shrinking quite fast..I'm just hoping it does represent the real position..not a guessed one and we find out MRO is really in a 8 hour orbit
Can't wait for the first pics to come down.. hope they pass over some of the "lost" landers and try to take pics sooner rather than later..
cheers
jb
Once they finish aerobraking, they raise periapsis out of the atmosphere and trim the orbit into the operational altitude. I think they have to jettison one <IR mapping spectrometer?> aperture cover, then do whole-vehicle checkout to evaluate systems (power, communications, thermal control.. etc) behavior in an orbit with day-night cycles, etc. Then do some systematic instrument calibrations.
Once they start operational measurements, they're going to concentrate observations in the latitude bands where observation conditions are best: optimum sun angle for imaging, maximum illumination for minerology mapping, minumum seasonal cloudiness, etc. As the seasons change and the equator crossing time rocks back and forth a bit relative to the nominal time due to Mars uneven seasons (eccentric orbit), they will have a specific observational campaign designed.
High priority is mapping observations of the Phoenix 2007 lander's landing zone candidates before north polar night arrives at the high latitudes of the targets.
Once they start operational measurements, they're going to concentrate observations in the latitude bands where observation conditions are best: optimum sun angle for imaging, maximum illumination for minerology mapping, minumum seasonal cloudiness, etc. As the seasons change and the equator crossing time rocks back and forth a bit relative to the nominal time due to Mars uneven seasons (eccentric orbit), they will have a specific observational campaign designed.
High priority is mapping observations of the Phoenix 2007 lander's landing zone candidates before north polar night arrives at the high latitudes of the targets.
QUOTE (edstrick @ Aug 6 2006, 02:34 AM)
Once they finish aerobraking, they raise periapsis out of the atmosphere and trim the orbit into the operational altitude. I think they have to jettison one <IR mapping spectrometer?> aperture cover, then do whole-vehicle checkout to evaluate systems (power, communications, thermal control.. etc) behavior in an orbit with day-night cycles, etc. Then do some systematic instrument calibrations.
The cover does not jettison. It is mechanical.
looks like the orbit is almost circular..and close to a 2 hour orbit..lets hope for update soon
circular orbit
circular orbit
The MRO webpage has new graphics for the orbit diagrams. There is also a countdown to something called "The Endgame" (only 37 hours away as I type this!). What could that refer to? Final orbits of aerobraking? End of the aerobraking? Boosting out of the aerobraking orbit? This is all very mysterious.
Endgame is a different name for the Walkout phase, which according to the MRO site, is the last five days of the aerobraking campaign (plus up to two weeks of trim maneuvers). Are they a month ahead of schedule? Unfortunately, science work is limited by solar conjunction, not aerobraking.
I''d have thought they would always schedule conservatively for aerobraking, and then just be a little more agressive if the opportunity presented itself given experience of early aerobraking passes.
Doug
Doug
QUOTE (akuo @ Aug 24 2006, 11:57 AM)
The MRO webpage has new graphics for the orbit diagrams.
Now this is what I was hoping for right from the start of the aerobraking!! Looks like they are way ahead of the process. Maybe they are getting good at this aerobraking thing or the orbiter is better designed then they had thought and could push the limits more on it. Only on orbit 373 where 500 was the figure that comes to mind for the initial number of orbits needed.
Either way, Now for the countdown to the new pics when they get the orbiter out of aerobrake mode
Maybe get a pic of Victoria crater same time Oppy gets there..that would be WAY cool . cheers
jb
They'll get out of Aerobraking.....get the proper orbit sorted...and then they'll be in conjunction so we won't get anything till about MER Sol 1000+
DOug
DOug
QUOTE (djellison @ Aug 24 2006, 04:23 PM)
They'll get out of Aerobraking.....get the proper orbit sorted...and then they'll be in conjunction so we won't get anything till about MER Sol 1000+
DOug
DOug
I know...But I can dream a little
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