What about http://pds-atmospheres.nmsu.edu/PDS/data/merimu_1001/ ?

That's true, but he was talking about MOLA gridded products, which are 16 bits.

It depends on what you want to do with the data as to how many bits you need. More recent versions of Photoshop do 16 bits. For altimetry, many applications make a shaded relief map in 8 bits from the original topo data.

Yes, but terminating it also saves the remaining development, launch, operations, and science costs, which probably total up to at least $150M if not more.

I hope for your server's sake that that code scales.

Seriously, this is a nice outreach effort but I'm not sure what Google's motivation or long-term commitment is. And what's with all of those gaps in the IR mosaic? (I guess I have to take the blame for the MOC mosaic looking like crap in spots.)

If you could drill down to individual MOC NA frames, that would be cool!

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

There are a few operational constraints; we're not allowed to point within 30 degrees of the Sun. I've been assuming that the half-phase, trailing-illuminated case is of most interest. Phil, does that sound right? I don't think I can sell a survey of phase angles, at least initially.

Thanks for the animation; very useful.

Rosetta, though the Mars flyby is a lot closer than I would have guessed, doesn't get all that close to Deimos, nor does the geometry look very favorable. See http://www.space.irfu.se/rosetta/sci/mars/
MEx would be able to do better on the occasion of a close flyby -- you'd think there would be some. (Edit: oops, no, the MEx orbit only goes a bit outside that of Phobos.)

Alas, since a slew is involved it'll take a bit longer to get this planned, but it seems like a worthwhile image, so I'll see if we can get it taken.

No. It's a lot easier for us to do this sort of stuff with MGS than it'll be with MRO; during aerobraking they're not going to perform imaging slews. (It was only the long suspension of aerobraking on MGS due to the SA damper problem that allowed the first MOC Phobos images to be done.) And I suspect it'll be a long time after MRO has gotten into mapping before they start doing stuff like slewing to image the moons.

We've thought about doing Deimos imaging with MOC, but the resolution possible from the mapping orbit is pretty bad; about 82 m/pxl at the closest approaches, and poorer that that for the ones where we wouldn't be shooting into the sun. But we can think about it again; if you can work out when and where we would improve the coverage over Viking that would help to sell it.

The current schedule shows the imaging happening on 3/22, but I'm not sure when the downlinking of the images will be finished, and there's still some schedule uncertainty depending on how the transition into orbital operations proceeds. It'll probably be better nailed down by the end of this week.

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.

I found the following about Celestia's SampledOrbits:

"The origin is the center of the parent object, whether it's a star or a planet. If the parent is a planet, the +z axis is the planet's north pole and the xy plane is the planet's equatorial plane at the reference epoch J2000. The x axis points at the ascending node of the equatorial plane on the ecliptic."

I believe this is the same inertial frame as the NAIF Toolkit's MARSIAU frame (not to be confused with the rotating IAU_MARS frame, alas.)

edit: for those of you still reading this obscure discussion, I think I was wrong: the Celestia frame is what we usually call Mars Mean Equator and Equinox of J2000, which is different from MARSIAU. Back to the drawing board.

Interesting to say the least.

The predict after TCM2 for closest approach during MOI was a little over 500 km. Note that the periapsis on the next orbit is typically lower by something like 80 km. They can raise this with a maneuver near the first apoapsis if needed.

The nominal burn is 26.8 minutes, of which 21.5 minutes are in view.

The minimum delta-V for capture is reached about 2 minutes after LOS.

Note that Horizons is outputting everything in heliocentric XYZ. If you did that for a Mars-orbiting spacecraft, then if Celestia's idea of where Mars is would have to match JPL's exactly, or the orbit would come "unstuck" from the planet. I'm pretty sure that the XYZ coordinates that Celestia uses should be Mars-centered. I'll have to get the source to see if it's oriented in J2000, but I seriously doubt that it is.

I couldn't find any documentation on this. The orbital elements are pretty clearly given in some central-body-equatorial system, but where the X vector is pointed wasn't clear to me. While possible, it seems unlikely that the Celestia developers settled on the IAU_MARS frame (IAU vector and Mars equinox of 2000)

BTW, there's a small MGS Mars map at http://www.msss.com/allmars.jpg (1440x720) so you don't have to keep using that old Viking map I'll see if I can't put a bigger one out soon.

No, wait a minute, you're right. I was assuming that the only way to put the orbit into Celestia was to supply orbital elements. I now see that there's an option to use "SampledOrbits" which are just the XYZ locations at some time spacing. Assuming that Celestia wouldn't choke with, say, a few months' worth of 5-minute or 1-minute spacing, one could write a program to extract that from the SPICE files. Then there's just the wrinkle of figuring out the coodinate system.

Certainly, but because there's no J2 perturbation modeling you would have to update the elements every 2-3 days to maintain their accuracy, which is a bit of a hassle and makes making an animation over the span of months a real pain.



Most of the plots of the repeat cycle I've seen zoom in and show orbit 1, orbit 2, and orbit N, where N in the length of the repeat (327 orbits nominal for MGS, IIRC, or a little under a month).

Of course, it's important to note that the repeat cycle is just an idealized case which usually doesn't happen exactly that way in practice. We never do MOC targeting a month out because the predicted ephemeris is just not accurate enough to support that.

I looked around but it looks like Aerospace Corp has continued to make it difficult to get SOAP, and I don't have a copy here, or I would try to help you out.

For the groundtrack walk, I could crank something with our targeting software.

I installed Celestia and it's not too bad, but for the fact that it only processes Keplerian orbital elements, which for spacecraft will stay accurate for a few days at best. And translating Mars orbits to the right coordinate system will be a somewhat painful bit of tedium (if you recognize the phrase "IAU vector and equinox of epoch", you know what I mean).

Here's an example of what Celestia shows for MGS and Odyssey. It's pretty, but the positions (based on some config files I found on the net) are fiction. And Celestia appears to save JPEGs flipped left-for-right. Oh well, so close!

Absolutely right, I stand corrected. At any rate, STK isn't likely to do what you want. It's too bad that no one has written a simple, general tool to do this stuff. Unfortunately, PDS doesn't seem to have released the source for their planet viewer tools -- http://pds-rings.seti.org/tools/index.html -- because that would be close to what one might want.

I didn't know it ever ran on anything but Windows.

STK probably isn't a great choice. I forget if the free version supports central bodies other than Earth. The SPICE file support, at least when I looked at this a few years ago, was fairly rudimentary and came in an expensive add-on package, like most other STK features.

It's somewhat surprising, but I don't know of a tool short of SOAP or STK, both of which have pretty steep learning curves, that do both of the things you want. Most targeting tools only draw groundtracks on maps, not on pretty 3D spheres. For public talks I've used Starry Night and faked the orbital elements. I've heard good things about Celestia, but I don't think it can use SPICE files directly, which you would really want for the groundtrack walk and the sun-sync orbit (both of which would require J2 perturbations to model correctly.)

MRO will routinely point off the nadir to image selected targets, but not as far as the limb. From the MRO website:

"The orbiter will typically keep its science instruments pointed to nadir (looking straight down at the surface). A few times per day, and for about fifteen minutes each time, the orbiter will point side-to-side in order to capture high-priority science targets that don't fall directly beneath the spacecraft. The spacecraft can point off-nadir up to 30 degrees."

There were some problems with the attitude simulation in some of the test files; perhaps this is what you are seeing.