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Mro On Approach, TCM-3 not required
mcaplinger
post Mar 1 2006, 05:33 PM
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QUOTE (helvick @ Mar 1 2006, 09:10 AM) *
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.


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.)


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Disclaimer: This post is based on public information only. Any opinions are my own.
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JRehling
post Mar 1 2006, 06:28 PM
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QUOTE (Steve @ Feb 19 2006, 03:27 PM) *
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


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.
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helvick
post Mar 1 2006, 06:55 PM
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QUOTE (mcaplinger @ Mar 1 2006, 05:33 PM) *
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.)

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.
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JRehling
post Mar 1 2006, 08:24 PM
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QUOTE (mcaplinger @ Mar 1 2006, 09:33 AM) *
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.


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.
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Bob Shaw
post Mar 2 2006, 01:24 PM
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QUOTE (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.)


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


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Joffan
post Mar 2 2006, 07:13 PM
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Has anyone heard or found any information on the TCM scheduled for 28 Feb?
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lyford
post Mar 2 2006, 08:39 PM
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QUOTE (JRehling @ Mar 1 2006, 12:24 PM) *
Consider the opposite.

Something like this? tongue.gif



(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....


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The Messenger
post Mar 2 2006, 09:57 PM
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QUOTE (Joffan @ Mar 2 2006, 12:13 PM) *
Has anyone heard or found any information on the TCM scheduled for 28 Feb?

"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
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djellison
post Mar 2 2006, 10:21 PM
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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
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yaohua2000
post Mar 2 2006, 11:15 PM
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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.

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RNeuhaus
post Mar 3 2006, 02:28 AM
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The next suspense time would be: tongue.gif

Times listed in Eastern.
Arrival at Mars
Mar. 10
NASA TV coverage: 3:30 p.m. - 5:45 p.m.

Rodolfo
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The Messenger
post Mar 3 2006, 02:52 PM
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QUOTE (djellison @ Mar 2 2006, 03:21 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

http://mars.jpl.nasa.gov/mro/mission/tl_approach_tcm.html
QUOTE
TCM-4: During the final approach to Mars, the orbiter will perform the last trajectory correction maneuver that will target the orbiter to its final aim point for Mars orbit insertion on a southern approach trajectory toward Mars. TCM-4 will be used to remove any errors from the previous trajectory correction maneuvers (TCM-1, TCM-2, and TCM-3) during cruise. It will target the final aim point for Mars orbit insertion and will occur about 10 days prior to that event.
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...
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Burmese
post Mar 3 2006, 07:06 PM
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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."
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Redstone
post Mar 3 2006, 08:10 PM
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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.
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djellison
post Mar 3 2006, 09:50 PM
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If they get away without TCM5 ( the last minute job ) then it will have been a quite outstanding navigation solution - TCM2 was a peach smile.gif

Doug
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