Unknown Object in Two NASA STS-103 Mission Photos

The unknown object is self-luminous and seems to be oval or disk shaped.

Official NASA photo (low resolution):

http://eol.jsc.nasa.gov/scripts/sseop/photo.pl?mission=STS103&roll=734&frame=59&QueryResultsFile=127076938358121.tsv

Streetcap1 managed to get hold of the high resolution UFO photo before NASA pulled it:

http://www.youtube.com/watch?v=J0Sm2a5Q_Dg

The NASA STS-103 Space Shuttle Discovery mission:

Launch date: 19 December 1999 -
Landing date: 27 December 1999.