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On July 23, 1972, the Earth Resources Technology Satellite (ERTS-1) was launched into space onboard a Delta 900 rocket from Vandenberg Air Force Base, California. ERTS-1 was the first Earth-observing satellite launched to monitor and study our planet's landmasses.
Also known as ERTS-A, the satellite was renamed Landsat 1 in 1975 and collected data until January 1978.
Landsat 1 orbited the Earth in a sun-synchronous, near-polar orbit (99.2 degrees inclination) at an altitude of 917 km (570 miles), circling the Earth every 103.34 minutes, completing 14 orbits per day. The satellite had a repeat cycle of 18 days and had an equatorial crossing time of 9:30 a.m. mean local time (+/- 15 minutes).
Landsat 1 data were acquired on the Worldwide Reference System-1 (WRS-1) path/row system, with swath overlap (or sidelap) varying from 14 percent at the Equator to a maximum of approximately 85 percent at 81 degrees north or south latitude.
Landsat 1 Instruments
Landsat 1 carried the Return Beam Vidicon (RBV) and the Multispectral Scanner System (MSS).
Return Beam Vidicon (RBV)
The RBV sensor utilized vidicon tube instruments containing an electron gun that read images from a photoconductive faceplate similar to television cameras. The data stream received from the satellite was analog-to-digital preprocessed to correct for radiometric and geometric errors.
- Collected about 1,600 sub-scenes
- 80 meter-ground resolution
- Three cameras operating in the following spectral bands:
- Band 1 Visible blue-green (475-575 nm)
- Band 2 Visible orange-red (580-680 nm)
- Band 3 Visible red to Near-Infrared (690-830 nm)
- Data recorded to 70 millimeter (mm) black and white film rolls
- Data: 3.5 MHz FM video
The RBV was supposed to be the prime instrument, but the MSS data were found to be superior. In addition, the RBV instrument was the source of an electrical transient that caused the satellite to briefly lose altitude control. It became necessary to shut down the RBV instrument in order to maintain the operation of the satellite.
More details about RBV data can be found on https://lta.cr.usgs.gov/rbv.html.
Multispectral Scanner (MSS)
The MSS sensors were line-scanning devices observing the Earth perpendicular to the orbital track. The cross-track scanning was accomplished by an oscillating mirror; six lines were scanned simultaneously in each of the four spectral bands for each mirror sweep. The forward motion of the satellite provided the along-track scan line progression.
- 80-meter ground resolution in four spectral bands:
- Band 4 Visible green (0.5 to 0.6 µm)
- Band 5 Visible red (0.6 to 0.7 µm)
- Band 6 Near-Infrared (0.7 to 0.8 µm)
- Band 7 Near-Infrared (0.8 to 1.1 µm)
- Six detectors for each spectral band provided six scan lines on each active scan
- Ground Sampling Interval (pixel size): 57 x 79 m
- Scene size: 170 km x 185 km (106 mi x 115 mi)
More information about MSS data can be found on https://lta.cr.usgs.gov/MSS.
Landsats 1, 2, and 3 were modified Nimbus meteorlogical satellites.
- Weight: approximately 953 kg (2,100 lbs)
- Overall height: 3 m (10 ft)
- Diameter: 1.5 m (5 ft)
- Solar array paddles extend out to a total of 4 m (13 ft)
- 3-axis stabilized using 4 wheels to +/-0.7° attitude control
- Twin solar array paddles (single-axis articulation)
- S-Band and Very High Frequency (VHF) communications
- Hydrazine propulsion system with 3 thrusters
Landsat 1 History (NASA Landsat Science)
ERTS-1 Launch picture (courtesy NASA)
Earth Resources Technology Satellite (ERTS) - 1973 (courtesy U.S. National Archives)
The Multispectral Scanner (NASA Landsat Science)