Uncontrolled Deorbit of Spy Satellite?

Recent reports indicate that a US surveillance satellite has lost power and is expected to make an uncontrolled reentry into the Earth's atmosphere in late February or March.

Since such satellites have the highest resolution when they are close to the ground, the satellites orbit at an altitude where there is significant atmospheric drag. To counteract this drag, the satellite is outfitted with a thruster, powered by the decomposition of liquid hydrazine fuel into nitrogen and hydrogen gas, to provide thrust which counteracts this drag. If the satellite loses power, it stops firing the thruster and the drag on the satellite causes it to sink deeper and deeper into the atmosphere, which increases drag. Eventually the satellite re-enters.

I would guess the risk of loss of data is pretty low here. All they have to do is design the satellite so that there won't be anything readable left upon reentry. I think we can do that. The memory shouldn't be too readable after being burnt up in the atmosphere, and modern spy satellites don't have any film. Hydrazine in the Earth's atmosphere would combine with nitrogen to form ammonia and be removed from the air by rain. It is conceivable that information could be gathered from debris about the materials used in the satellite which could be useful to people designing their own satellites.

The spacecraft, known as "USA 193", NROL-21, or object number 29651, was launched December 14, 2006, from Vandenberg Air Force Base near Lompoc in southern California. The orbital characteristics fit those of a "Lacrosse" Earth-observing radar satellite:

"Perigee: 354 km (219 mi). Apogee: 376 km (233 mi). Inclination: 58.50 deg. Period: 91.83 min. COSPAR: 2006-057A. USAF Sat Cat: 29651. Classifed NRO mission of uncertain objectives, possibly military observation with a mixed payload. The ground track nearly repeated every 2 days (30.92 revs), enabling frequent revisit of targets of interest. The first four Lacrosses behaved similarly (28.9 revs in 2 days). and Lacrosse 5 made 43.05 revs in 3 days. Keyholes nearly repeated every 4 days; NOSS every 4 days."

The orbital characteristics are well-known- in fact, amateur astronomers take pictures of them passing over all the time. In fact they even can take ones good enough to reveal that the solar panels aren't there. The one at the top of this post has panels- they extend from upper left to lower right.

Lacrosse radars are believed to offer radar images with one-meter resolution through clouds or at night, a major advantage in a time-critical mission such as bomb damage assessment. However, there are only five of the things and the other side knows where they all are, and each one passes over a given spot about once every two days.