But we knew that one mirror could not do the whole job. After Telstar I had been in orbit more than 30 days, the 68-degree mirror would only be in position to give infrequent flashes, and one at about 95 degrees would be more useful. This presented two problems. First, no facet on the satellite makes a 95-degree angle with the spin axis. However, we could use one of the facets just below the equatorial antenna, which makes a 112-degree angle, and groove or _facet_ the mirror so that its reflecting faces became narrow strips slanted 17 degrees away from the base at the angle of 95 degrees (112 - 17 = 95). Our second problem was space—since there was not enough room left on any of the 112-degree facets to mount a second large mirror, we substituted two smaller mirrors and mounted them 120 degrees apart. This arrangement lets us know from which mirror we see flashes—the plane mirror gives one flash for each revolution of the satellite; the faceted mirrors give two flashes for each revolution of the satellite. [Illustration: _Sketches of three reflecting mirrors and their locations on the Telstar satellite. The upper plane mirror is set at 68° to the spin axis; the lower ones are faceted to give reflecting surfaces at 95°. Two of the satellite’s six solar aspect cells can be seen within the circular cut-outs in the mirrors._] How We Record Flashes from the Mirrors Now we had finally found a satisfactory way to reflect a train of tiny flashes—much too faint to be seen by the naked eye—from Telstar as it passed across the sky during the night. But our main aim was to record the exact times when these flash bursts occurred. With this information, we could, using the method we described above, tell very accurately both the satellite’s spin axis and its rate of spin. We do not have space to describe the many problems that had to be solved in setting up the equipment to record the flashes. Let us merely outline the procedure that we finally devised: 1. _To pick up the satellite’s flashes we use a 12-inch-aperture photoelectric telescope mounted on a radar trailer (shown in illustration below). It is pointed by means of prediction drive tapes produced by an electronic computer; these are based on data from previous passes._ 2. _On clear, dark nights when the satellite is at relatively short range, we can see it with an auxiliary finder telescope, and then adjust the large telescope precisely. Or, if the satellite’s high-frequency beacon has been turned on, the Holmdel microwave antenna can automatically point our large telescope._ 3. _When flashes of light are picked up by the telescope, they fall directly onto the cathode of a photomultiplier tube. They are then filtered out from the random light in the night sky and amplified._