2001 Mars Odyssey - PIP QA

1. What data volume is available, and how much is already allocated?

The expected data volume during the 917-day science mission, broken down by instrument is:

No other formal data volume allocations exist.

2. For the VIS CCD array, what is the integration time per pixel? Is it fixed, or variable?

The integration time can be commanded for each VIS image. The nominal integration time for the mapping orbit at Mars will be approx. 6 msec. It is adjustable in increments of 0.1 msec. The maximum integration time is dependent on the VIS interframe time which is nominally set at 1 sec. This results in approx. 25 rows of overlap between each frame. For this interframe time the maximum integration time is approx. 100 msec. It is not planned to adjust the interframe time unless it is required to adjust the overlap.

3. For the VIS CCD array, can pixels be averaged? Is it possible to upload a software filter to decide whether to queue an image for transmission to Earth?

Spatial summing is allowed for VIS images. The possible options are 1x1, 2x2 or 4x4. No onboard image analysis or image queuing capability is included in the existing flight software.

4. THEMIS, like MOC, is a nadir-pointed camera. Like MOC, will there be opportunities to point substantially off-nadir to accomplish specific science objectives? If so, what amount of off-nadir pointing can be accommodated? Or, would a PS proposal requiring off-nadir pointing be considered a demonstration of lack of knowledge of the mission's technical capabilities?

Off-nadir THEMIS observations are not currently baselined. However, there are no major technical obstacles to performing the required spacecraft maneuvers to obtain off-nadir imaging, as is being done on Mars Global Surveyor. The amount of off-nadir pointing that could be accommodated would be determined in consultation with the affected instrument teams, the spacecraft team and project management.

5. The appendix describing PDS archiving is somewhat generic in terms of specifying exactly what data and ancillary material will be archived for each instrument. About the only thing I saw that was instrument-specific was a breakdown of expected data volumes from each instrument. Should I take this to mean that the details of how a particular instrument's data will be archived (what fields will be saved in the headers, what format the data files will take, what constitutes Levels 0, 1A, 1B, etc. for a particular instrument) have not yet been decided and are therefore a valid place where I could propose to make a contribution? Or, are these kinds of particulars already decided and were just left out of the PIP appendix?

Archiving of Odyssey's instruments' science data is described in a set of documents and notes that can be accessed at: http://wufs.wustl.edu/missions/odyssey/ Much of the work is incomplete at the current time, but is expected to be completed by the start of mapping. Therefore, the details of the instrument data structures (headers, Level defintions, etc.) should be in place by the time the Participating Scientist selections are complete. Such work does not appear to be appropriate as a task in a Participating Scientist proposal. Tasks such as calibration, validation, and verification, would be appropriate.

6. The PIP gives no indication of the intended radiometric calibration scheme for THEMIS, other than brief mention of an "internal flag" that will provide calibration and sun-screening. For calibration of the thermal subsystem, has the emissivity spectrum of this flag been measured, and will there be some way of knowing its temperature? Is there any kind of calibration blackbody, similar to what TES has? Alternatively, are there plans to slew the spacecraft to observe standard IR stars for calibration?

The emissivity spectrum of the calibration flag has been measured. The temperature of the flag can be monitored during instrument operations. The flag serves as the calibration target. There is no other "calibration blackbody." There are no plans to use stars as IR calibration targets.

7. There is an inconsistency in the size of the thermal images. The second bullet at the top of section 4 specifies the images will be 320x320 pixels, but elsewhere in the PIP, the image size is described as 320 pixels cross-track by 240 pixels along-track. Which is it?

All THEMIS IR images are 320 pixels wide (cross-track). While the IR detector is 240 pixels along-track, the instrument acquires frames continuously. Thus the along-track image dimension is selectable; it can be hundreds up to thousands of pixels long.

8. Can the THEMIS IR and VIS detectors image the same area on Mars at the same time?

Yes, with limitations. The VIS cross-track footprint is 18.4 km, versus 32 km for the IR. In the along-track direction, the VIS frame size is limited by its 4 Mbyte data buffer size. The along-track dimension can be 15-65 km, depending on the number of bands used (65 km is the maximum for a single-band image). On any given swath, the VIS data must "wait" for the IR data collection to finish before being transferred to the spacecraft, since the VIS and IR share a single high-rate data interface.