I was on my way to work headed south from Tularosa to Alamogordo, New Mexico. At the time I was working at the Radio Shack in the White Sands Mall. So it must have been around 12:00 PM. Usually I take US 70/54 but decided to take the rail road access road just because it was a change of pace. The road is a slow road 50-mph max. I spotted a black object that at I first thought was a water tank. The kind that supplies water to cities and I wondered when they had put up a tank. But then I realized it was too high in the air and it had no support structure. I would say the object was between 80 to 200 feet off the ground, moving slowly north to south approximately 30 to 50 mph. It was probably somewhere between highway 70/54 and Holoman AFB property line. I thought it might be a balloon, but if it was it was a very ridged structure. I saw no rotation, and could not make out any detail other than it was black and had a configuration like a water tank. I followed it almost all the way into Alamogordo when it began to descend, it landed in a grove of trees beyond what is called the La Luz gate that lets employees onto Holoman AFB. The access gate was locked so I was unable to get any closer than that. When it landed I noticed a blue airforce pick up drive towards it. I was unable to see much more because it disappeared behind the trees so I could not see any kind of recovery crew. The object descended slowly in the manner of a hot air balloon but with much finer control. Its controllability was not erratic at any time, nor did it act as a balloon would act. Prevailing winds are from southwest to northeast so it would have been going directly against the wind. I saw no emergency vehicles or any indication of what was happening was unexpected. My assumption however unusual the sighting was and it still is my assumption that it was some kind of experiment conducted by the Air Force. I have never see an object like it before or since. But to be honest I haven't been looking. I couldn't tell you if it made noise because it was too far away - to no more than a mile away and I had (old car lots of noise) car engine noise. When I stopped at the La Luz gate and watched it land I didn't hear any noise, but at that point it was still a good mile away. Winds would have been such that the sound would have not carried to me unless it was extremely loud. My times and dates may be off by a lot because I am trying to remember something that happened several years back. I have 22 years experience in the airforce as an Aircraft Mechanic, and I am aware of most but not all aircraft configurations. Slow steady direction, no visible changes or erratic movement. Flight level was constant until it reached La Luz gate then it did controlled and easy decent. If I had held my arm out I could have covered the object with the end of a pencil eraser. I would say judging by the trees it went behind it was 25 to 30 feet wide and about the same tall.