LES-1
From Wikipedia, the free encyclopedia
 Image of Lincoln Experimental Satellite (LES) 1 | |
| Mission type | Communications satellite |
|---|---|
| Operator | USAF |
| COSPAR ID | 1965-008C |
| SATCAT no. | 01002 |
| Mission duration | 60 years, 7 months, 26 days (elapsed) |
| Spacecraft properties | |
| Manufacturer | Lincoln Laboratory |
| Launch mass | 31 kg (68 lb)[1] |
| Start of mission | |
| Launch date | 11 Feb 1965, 15:19:05 UTC |
| Rocket | Titan IIIA |
| Launch site | Cape Canaveral LC20[2] |
| Orbital parameters | |
| Reference system | Geocentric |
| Regime | Low Earth |
| Eccentricity | 0.00109 |
| Perigee altitude | 2,780 km (1,730 mi) |
| Apogee altitude | 2,803 km (1,742 mi) |
| Inclination | 32.1° |
| Period | 145.80 minutes[1] |
| Epoch | 11 Feb 1965 |
Lincoln Experimental Satellite 1, also known as LES-1, is a communications satellite, the first of nine in the Lincoln Experimental Satellite program. Launched by the United States Air Force (USAF) on February 11, 1965, it pioneered many then-advanced technologies including active use of the X Band (7 to 11.2 GHz) to service hundreds of users. LES-1 did not have a successful operational life due to being placed in a suboptimal orbit, and it ceased transmissions in 1967. After 45 years of inactivity, LES-1 spontaneously resumed transmissions in 2012 making it one of the oldest zombie satellites.
The Lincoln Experimental Satellite (LES) series was MIT's Lincoln Laboratory's first active communications satellite project. Lincoln had previously successfully developed and deployed Project West Ford, a passive communications system consisting of orbiting copper needles. The goal of LES was to increase the transmission capability of communications satellites ("downlink"), which was necessarily constrained by their limited size. After receiving a charter in 1963 to build and demonstrate military space communications, Lincoln focused on a number of engineering solutions to the downlink problem including improved antennas, better stabilization of satellites in orbit (which would benefit both downlink and "uplink"—communications from the ground), high-efficiency systems of transmission modulation/de-modulation, and cutting-edge error-checking techniques.[3]: 81–83
These experimental solutions were deployed in a series of nine spacecraft called Lincoln Experimental Satellites (LES). Concurrent with their development, Lincoln also developed the Lincoln Experimental Terminals (LET), ground stations that used interference-resistant signaling techniques that allowed use of communications satellites by up to hundreds of users at a time, mobile or stationary, without involving elaborate systems for synchronization and centralized control.[3]: 81–83
The first, second, and fourth satellites in the LES series were designated "X-Band satellites," designed to conduct experiments in the 7 to 8 GHz spectrum of the X Band, a small section of the SHF (super high frequency) band (7 to 11.2 GHz)[4]: 9–2 because solid-state equipment allowed for comparatively high output in this band, and also because the band had been previously used by Westford.[3]: 83–84
Spacecraft design
Polyhedral in shape, the 5 ft (1.5 m) spacecraft drew power from 2,376 solar cells, operating only in daylight. LES-1's primary experiments were a solid-state 0.1-watt transmitter, a multiple antenna system switched on by one of the satellite's four optical Earth sensors, and a magnetic coil attitude system. Eight semi-directional horn units evenly spaced around the satellite comprised the antenna system.[5]
The spacecraft was designed to last two years, during which it would be used for communications experiments conducted between stations in Westford, Massachusetts, and Pleasanton, California.[5]
