I believe that wub has the reason - the USAF wanted to fly it during the day, hence release of a photo.
The photo was a carefully ambiguous image released by the Pentagon in November 1988. after the Presidential elections, and which suggested that the jet was short and fat. That's the image green granite is referring to, I'm sure - this one:
Prior to that there had been NO public domain images of the aircraft, and any artists' impressions and plastic kits had the shape entirely wrong. None had facets, for a start - the best known "Stealth Fighter" shape of the time was a plastic kit from Testors, which was curvacious, with inward canted twin fins and canards.
If any previous pictures had existed then in the public domain, they'd be available now on the Internet (e.g. on
this site), but they don't - QED.
Sure, there had been rumours for years (carefully leaked to bug the Sovs?) that such a thing existed, but what it actually looked like was anybody's guess.
It wasn't until several months after the Pentagon image was released that Aviation Week published the first clear pictures of the jet in the circuit at Tonopah Test Range (TTR) during the day, and not until Spring 1990 before the USAF released official pictures and publicly displayed a couple at Nellis.
It's interesting to note that, according to Steve Davies' excellent book "Red Eagles" about the only recently admitted-to MiGs operating at TTR during the day at the same time as the unacknowledged F-117s were flying at night, the MiG pilots were officially unaware of what exactly it was operating from the other hangars on the base.
The first F-117 flew in 1981 (after the smaller proof of concept 'Have Blue' which first flew in 1977), and the non-trials aircraft moved to TTR by 1983, so flying an semi-operational unit of 10s of aircraft for 5+ years without anybody publicly knowing what the thing actually looked like was quite an achievement.
It's still a mysterious aircraft. Officially all retired in 2008 (and most stored in their original TTR hangars), video of an airworthy F-117 over Nevada was taken in October last year...
PS Surely everybody knows that Aurora was replaced by Blackstar?
