Deimos on the 'left' (actually west) side of Mars. This is from the set on day 51 at 1900 UT. (Our pictures have an east-west flip in this geometry.)

The Optical Navigation Camera is functioning as predicted on approach to Mars on the MRO spacecraft. It is sensitive to trajectory errors at about the 1 microradian level (times the distance to Mars, so for example, roughly 5 km at 20 days before MOI. ).

We have acquired 180 frames on approach between February 9 and Feb 22. The camera and spacecraft have performed without a problem. There are about 300 frames between now and March 7th when the distance will be less than one million km.The trajectory estimates including optical are consistent with those obtained from the ground-based radion data.

The camera routinely detects 10.3 mag stars. We had originally planned to rely on 3 or 4 stars per picture of 8.5 mag but we have as many as 30 stars in the field with useable signal-to-noise ratios of 5 to 1 or more. These allow us to constantly check our distortion model.

Although it seems very significant in the highly "stretched" frames, the stray light is very small compared to the original version of the camera. All the work we did has been successful for this application and we are getting good opnav accuracies ( ~ 0.05 to 0.07 pixels and we not done refining yet). As I mentioned at the MPSET, Mars is just 0.01 to 0.02 degrees (or 7 to 14 ONC pixels) off the field of view of the camera in these early frames.

Although it may seem surprising, for the OS detection situtation, this level of stray light supression may be all that's necessary because Mars will be 3 degrees away from the edge of the field. However Mars will of course be much larger. However a lot of Mars will be very far from the optical axis.

For the OS detection problem we have a lot of interesting work to do to understand whether and how the camera should be modified.

As you can see from the pictures below, we are starting to see Deimos orbital errors in Deimos's data, that is, oscillatory residuals.

We always shaved the pointing to keep Mars out of the field by just 10 to 15 ONC pixels so we could get Deimos over as wide a range of orbital longitudes as possible, even at millions of km. Great pointing job!

Click image for larger image.

Pic 1: Deimos on the 'left' (actually west) side of Mars. This is from the set on day 51 at 1900 UT. (Our pictures have an east-west flip in this geometry.) Deimos is beyond Mars and heading behind it	Pic 2: Occurs about 9 hours after pic1 and shows Deimos after it has popped out of the glare again. It is still farther from the s/c than Mars is. Deimos is on the right, stars on the left.	Pic 3: Shows the scene about 15 hours (or half an orbit) after pic 2. Deimos has crossed in front of Mars and moved into the observable region far enough angularly from Mars to be seen again.
Zoom 1: Show the little box near Deimos where zoom1 is in the first pic of the 12 , and zoom1a is in the last of the same set. Deimos's motion relative to the stars is ~ 10 pixels and is clearly visible. The brighter star toward the right is 8.5 mag, the fainter on near the top about 9.3.	Zoom 1a: Show the little box near Deimos where zoom1 is in the first pic of the 12 , and zoom1a is in the last of the same set. Deimos's motion relative to the stars is ~ 10 pixels and is clearly visible. The brighter star toward the right is 8.5 mag, the fainter on near the top about 9.3.	Zoom 3: Compare zoom1 to zoom3 to see that Deimos (near the bottom center of zoom3) in pic 3 has not yet caught up to it's position in pic1. (It's only 24 hours after pic1 and the period is about 30 hours.) It's still heading out away from Mars before 'falling' back in again to its pic 1 position. The orbital longitude difference between pic 1 and pic 3 is about 72 degrees, that is, Deimos in pic3 trails the position in pic1 by 72 deg.