26 August 1999 image Transit of Phobos from Mars

the penumbral shadow of phobos on martian landscape, seen mars global surveyor on 26 august 1999. center of shadow @ 10.9°n 49.2°w @ 04:00:33 utc

far more detailed images of shadow taken arrival in 1997 of mars global surveyor , high-resolution mars orbital camera. 1 such image taken on 26 august 1999 , shows shadow @ high resolution. image featured in 1 november 1999 nasa press release.

by examining maps of mars see shadow centered @ around 10.9°n 49.2°w.

we can original image files @ m04-03241 (red) , m04-03242 (blue), part of gallery of moc wide-angle images, region lunae palus, subphase m04. image start time 03:26:13.01 utc, line integration time 80.4800 milliseconds, , downtrack summing factor 4. since shadow centered @ 6400 pixels bottom of original 10800-pixel-high image (mars global surveyor had south-to-north sun-synchronous orbit), add (6400 × 0.08048 × 4) = 2060.3 seconds = 34 minutes 20.3 seconds time of 04:00:33.3 utc center of shadow. putting in longitude/latitude/altitude coordinate values -310.8,10.9,0 into

jpl horizons see predicted time of mid-transit 04:00:36 utc, in perfect agreement within error of determining exact longitude , latitude of center of shadow. 14:41 martian local solar time, , sun s altitude 46.5° above horizon. jpl horizons shows on 26 august 1999 distance between earth , mars 9.6 light-minutes.