"Moving 1,400′ downrange from the Antenna Array, we come to Antenna Pit 1. At this location, test objects can be placed upon four different mounts. The support may be either a 14′ long metal or composite pylon, a foam column, or an inflated air column. The targets mounted at Pit 1 may be up to 14′ in length and weigh up to 1,600 pounds. The targets here are placed upon the mount using either a crane or forklift.

Immediately uprange of Pit 1, visible on the surface of the range, is a long white metal cover. Under this cover is a hinged calibration pylon. Prior to testing a model at Pit 1, the calibration pylon is extended with a known, measured shape mounted on it. The technicians at the operations complex can then adjust and calibrate their equipment on the basis of a known shape. The calibration pylon is then retracted and an actual model measured.

Moving next to a point 5,000′ from the antenna array, we come to Pit 2. This 80′ deep pit is covered by hinged white doors on the surface and contains a pylon extended by means of a hydraulic ram. Just beneath these doors, and above the retracted pylon is a small workroom in which models up to 50′ in length and weighing up to 6,000 pounds may be mounted to the pylon. Immediately adjacent and uprange to Pit 2 is a much smaller pit containing a calibration shape mounted on a hinged pylon. It functions in the same manner as the calibration pit for Pit 1.

This is pretty much the limit of the first phase of the facility at Helendale. But then in 1985, work began to extend the range and the major bells and whistles were put in.

A large 60′ diameter mobile antenna on a crawler-type transporter was added 5,300′ from the main antenna array. When not in use, the transporter moves the large dish antenna laterally, off to the west side of the range. This massive antenna required a specially constructed roadbed and bridge over a flood control channel. The antenna, known as MOBATS, is used for low frequency, high power RF measurements. This mobile crawler antenna seems to be a replacement for an antenna pit planned at the 5,400′ point, but never implemented.

At the 7,300′ mark, we come to a very long white metal cover in the surface of the range. Beneath it is another calibration pit (Area 50), the largest of the range at 130′ long. As with the other calibration pylons, a simple methodology is used to raise it. The pylon is merely hinged at one end, and after the cover doors are opened, it is elevated from its horizontal resting position within a well to a near vertical position. Again in this case, its purpose is to place an object of known shape and size into the radar beam to calibrate the receiving equipment prior to actual model testing.

The jewel of the facility is found at the 7,500′ point. This curious structure, in the depression at the far end of the range, is known as the “Upper Chamber” (or Area 30 during construction). Although it appears to be built of solid concrete, it is actually composed of concrete blocks. On the side of the structure with the vertical face, there is a large, side-sliding hangar door in the 40′ high face of the structure. It is through this door that models are brought into the Upper Chamber.

Careful inspection of the Upper Chamber’s roof reveals what appears to be a square cover, 80′ on a side, with a split along a diagonal. This cover retracts on two sides, separating along the diagonal, exposing an 80′ square opening into the Upper Chamber below. When closed, an air bag arrangement seals the diagonal seam.

Surprisingly, the useable area within the Upper Chamber is less than it appears when viewed from outside. Actual level floor space is only about 130′ by 110′, about 14,000 square feet. Most of the area apparently covered in concrete surrounding the Upper Chamber is actually covered slope. At the time of construction this area was not utilized and left as covered, but bare slope."