The topics listed here describe the items that are in each ".tab" Ancillary Information table. Think of these as the column headers for the .tab table. Of interest to many users will be the latitude and longitude of the image; please note that these and all other data presented in the .tab files are approximate and have not been validated. These values are subject to refinement when the data are archived with the NASA PDS.
Additional information about the information in these columns can be seen in columndescript.txt and by examining MGS MOC data release information at the NASA Planetary Data System; see also the or the PDS Mars Global Surveyor Mars Orbiter Camera (MOC) Image Collection.
Column Headers for .tab files:
1. volume id -- not relevant for pre-archival products
2. file name -- not relevant for pre-archival products
3. product id -- i.d. number for the image: note that XXX/YYYYY should be read as XXX-YYYYY
4. SCET time at start of image -- time the first line of the image was acquired; YYYY-MM-DD-time
5. instrument name -- NA= narrow angle MOC camera, WA= wide angle MOC camera
6. filter name (RED or BLUE, N/A for NA) -- there is no color filter for the narrow angle camera
7. image width -- number of pixels wide
8. image height -- number of pixels high
9. crosstrack summing. For global images the crosstrack summing is variable across the detector. Please refer to the mocsis.txt appendix F for a full description. -- Public targets are either summed 1 (for ~1.5 m/pixel), summed 2 (for ~3.0 m/pixel) or summed 3 (for ~4.5 m/pixel)
10. downtrack summing --Public targets are either summed 1 (for ~1.5 m/pixel), summed 2 (for ~3.0 m/pixel) or summed 3 (for ~4.5 m/pixel)
11. image resolution in meters/pixel at center of image -- If the aspect ratio of the image is 1, or nearly 1 (e.g., 0.96), then the resolution is the same in cross track and down track directions; if the image has an aspect ratio greater than 1 (usually ~1.25 or ~1.50), then the downtrack resolution is poorer than the cross track (multiply the aspect ratio times the cross track resolution to estimate downtrack resolution)
12. pixel aspect ratio (pixel height/pixel width) at center of image. The image's center pixel is projected on the ground and its linear extents are ratioed, so any effects of emission angle and line time are modelled. To recover an image with 'square' pixels, the image should be resampled to a height of aspect_ratio * input height. -- aspect ratio, which for public targets will usually be near 1.0, but in some cases may be ~1.25 or ~1.50 in the downtrack dimension
13. emission angle at center of image
14. incidence angle at center of image
15. phase angle at center of image
16. center longitude
17. center areographic latitude
18. upper left longitude
19. upper left areographic latitude
20. upper right longitude
21. upper right areographic latitude
22. lower left longitude
23. lower left areographic latitude
24. lower right longitude
25. lower right areographic latitude
26. mission phase name -- the phase the MOC mission is in; images with prefix Rxx are in the Relay phase; images with Exx are in the Extended phase; etc.
27. target name (e.g., MARS, PHOBOS, STAR, SPACE)
28. spacecraft clock value at start of image
29. focal plane temp in Kelvins
30. line integration time in milliseconds
31. gain mode (see documentation)
32. offset mode (see documentation)
33. first pixel stored from detector, zero-based
34. A description of the compression applied to this image, of the form string-parms, where
35. image width from left to right image edge in km
36. image height from first line to last line in km
37. distance from spacecraft to closest point on surface in km
38. distance from spacecraft to target body center in km
39. range from spacecraft to intersection of view vector with target body in km
40. Because of the MOC's line-scan nature, depending on the orientation and sense of rotation of the spacecraft and the optical inversion properties of the camera system involved, MOC images can either be normal or flipped left-for-right (independent of whether the image is north up or south up.) This flag will be 'F' if the image should be flipped left-to-right, and 'N' if it is already in normal form. 41. The angle in degrees clockwise from the reference axis of the image (a line from the center to the right edge of the image) to the direction to the north pole of the target body. If the USAGE_NOTE described previously is 'F', the image should be flipped prior to applying this angle. 42. The angle in degrees clockwise from the reference axis of the image (a line from the center to the right edge of the image) to the direction to the subsolar point on the target body. If the USAGE_NOTE described previously is 'F', the image should be flipped prior to applying this angle.
43. west longitude of subsolar point in degrees
44. planetographic latitude of subsolar point in degrees
45. west longitude of subspacecraft point in degrees 46. planetographic latitude of subspacecraft point in degrees
47. distance from the center of the image on the target body to the center of the sun in km
48. solar longitude ('L sub s') at time of image in degrees from martian vernal equinox, as computed by the method in 'Accurate analytic representations of solar time and seasons on Mars with applications to the Pathfinder/Surveyor missions', Michael Allison, Geophysical Research Letters 24, 16, pp 1967-1970 (August 15, 1997) 49. Local True Solar Time in decimal hours from midnight at the center of the image, as computed by the method in 'Accurate analytic representations of solar time and seasons on Mars with applications to the Pathfinder/Surveyor missions', Michael Allison, Geophysical Reseach Letters 24, 16, pp 1967-1970 (August 15, 1997). An 'hour' in this context is an angular measure of 15 degrees of solar motion.
50. The image skew angle is the absolute value, in degrees, of the angle between the left edge (a line between the lower left and upper left corners) and the bottom edge (a line between the lower left and lower right corners) of the image, where the edges are projected on the target body. For images whose footprints are exactly rectangular, this angle will be 90 degrees. Departures from 90 degrees indicate a non-rectangular image footprint, caused by slews of the spacecraft during imaging outside the orbit plane or off-nadir pointing, or both.
51. A text description of the scientific purpose for the acquisition of this image. For routine mapping operations, this will most likely be the goal of the image as targeted (which may not be met if the image missed its target significantly, the atmosphere was cloudy, gain parameters were set inappropriately, etc.)
52. 'OK' if all fragments of the image are received without detected checksum or sequence errors, and 'ERRORS' otherwise.
53. orbit number as defined by the MGS Project