LACE (satellite)
The Low-Power Atmospheric Compensation Experiment (LACE), also referred to as LOSAT-L and USA-51, was a military satellite developed by the Naval Research Laboratory for the United States' Strategic Defense Initiative in the late 1980s and early 1990s, otherwise referred to as the "Star Wars" program.[4]
"LOSAT-L" redirects here. For the anti-tank missile system, see MGM-166 LOSAT.Names
LOSAT-L
USA-51
Technology demonstration
20496
3 years
3,175 pounds (1,440 kg)
Body: 1.2m x 1.2m x 2.4m (height)
February 14, 1990, 16:15:00 UTC
LC-17B, Cape Canaveral Air Force Station[1]
McDonnell Douglas Space Systems
April 15, 1990
Decommissioned
February 14, 1993
May 24, 2000
0.00123
532.00 km (287.26 nmi)
549.00 km (296.44 nmi)
43.000 degrees
95.30 minutes
1990-02-14 00:00:00 UTC[2]
Ultraviolet Plume Instrument (Plume Camera)
Makutsov-Cassegrain
10 cm
600 cm
78 cm2
195-300 nm
Background[edit]
The LACE mission concept began in February 1985 when the Strategic Defense Initiative Organization approached the Naval Research Laboratory to develop an experiment to characterize laser signals transmitted and received through the Earth's atmosphere from a ground station to an orbiting experiment. The laboratory had been involved with spaceflight since the dawn of the space race, having led the Navy's Vanguard program up until 1959. Since then the laboratory had developed satellites to perform experiments relating to solar radiation, radio transmission through the ionosphere, gravity gradient stabilization, and ocean surveillance, among others.[5]
In July 1985, the Laser Communication Experiment (LACE) began development. The simple, spaceborne experiment was planned to be flown on the next flight of NASA's Long Duration Exposure Facility (LDEF), launched aboard the Space Shuttle. Because the LDEF was a completely passive payload, LACE would've required additional power and communication subsystems to function properly. After the Challenger disaster, shuttle launches were delayed indefinitely, and the LDEF would remain in orbit from the beginning of its first mission until 1990. This led to the further development of LACE into a full satellite by June 1986, and the availability of expendable launch vehicles such as the Atlas, Titan, and Delta rockets to launch government payloads such as LACE. The satellite would later be renamed to be the Low-power Atmospheric Compensation Experiment. [6]: 2 [7]: 1
Before launch, LACE was placed in the Delta II's payload fairing alongside the Relay Mirror Experiment (RME) satellite. Also known as USA-52 and LOSAT-R, it was also sponsored by the SDIO for ground-to-orbit laser tests and was built by Ball Aerospace.[8] The two satellites and a third, LOSAT-X, were originally meant to be launched together, and were all part of the SDIO's LOSAT (LOw-altitude SATellite) program, even though they all had different designs and missions. LOSAT-X was removed from the launch manifest and would launch the following year with the GPS satellite USA-71.[9]
Spacecraft[edit]
LACE did not have any onboard propulsion systems, instead, it relied on gravity-gradient stabilization to keep its experiments pointed towards Earth. It accomplished this using three 150 ft (46 m) long booms pointing along the forward, rear, and zenith axes of the spacecraft relative to the direction of its motion. While the zenith boom would remain fully extended during normal operation, the two booms along the forward and rear axes were designed to be extended and retracted 125 times during the 30 months of LACE's planned mission, and successfully did so over 65 times, albeit most movements were minor. The three booms were the largest retractable booms ever flown in space at the time of LACE's launch in 1990.[10][11]: 252 [7]: 3, 10–12
Instruments[edit]
Sensor Array Subsystem (SAS)[edit]
The Sensor Array Subsystem was the primary payload of the LACE satellite. It contained three sets of sensor arrays with a total of 210 sensors designed to detect laser emissions on-orbit from visible, pulsed, and infrared lasers on Earth.[12]
The visible sensor array had 85 sensors distributed in the center of the earth-facing "target board". It was specifically designed to detect laser emissions from the Short Wavelength Adaptive Techniques (SWAT) program's argon ion laser at the Air Force Maui Optical Station (AMOS) in Maui, Hawaii. The array was sensitive to laser emissions between 400 nanometers (nm) to 1.06 micrometers (μm). Before launch it was calibrated for the SWAT laser's wavelength of 514.5 nm, which was designed by the MIT Lincoln Laboratory. Later in the mission, this array was re-calibrated to 1.06 μm to support the USAF Starfire Optical Range at Kirtland AFB, New Mexico.[7]: 6
The pulsed array's 85 sensors were located in the same housings as the visible array sensors. They were calibrated at 354 nm and 1.06 μm, and were designed to generally support pulsed excimer lasers at wavelengths from 300–400 nm and a low-power laser emulator at 1.06 μm. The array detected pulses of durations from 10 nanoseconds (ns) to 2 microseconds (μs) with a maximum repetition rate of 100 pulses per second.[7]: 6
Like the visible array, the infrared array was also designed for a specific laser program: the Low Power Chemical Laser (LPCL) at White Sands, New Mexico. The array's 40 sensors were distributed uniformly across the target board, and detected deuterium fluoride chemical laser emissions between 3.6 and 4.0 μm.[7]: 7