Landsat Missions

Landsat 7

Landsat 7 was launched from Vandenberg Air Force Base in California on April 15, 1999 on a Delta II rocket. The satellite carries the Enhanced Thematic Mapper (ETM+) sensor.

Since June 2003, the sensor has acquired and delivered data with data gaps caused by the Scan Line Corrector (SLC) failure.

Landsat 7 Launch

Landsat 7 Launch
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Explore More Landsat 7

Explore More Landsat 7
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Illustration of Landsat 7 in orbit

A Rendering of the Landsat 7 Satellite. 

The Landsat 7 satellite orbits the the Earth in a sun-synchronous, near-polar orbit, at an altitude of 705 km (438 mi), inclined at 98.2 degrees, and circles the Earth every 99 minutes.  The satellite has a 16-day repeat cycle with an equatorial crossing time: 10:00 a.m. +/- 15 minutes.  

Landsat 7 data are acquired on the Worldwide Reference System-2 (WRS-2) path/row system, with swath overlap (or sidelap) varying from 7 percent at the Equator to a maximum of approximately 85 percent at extreme latitudes.  

Visit Landsat Data Access for information on accessing products created from data acquired by the sensors onboard the Landsat satellites.

 

 

 

 

 

 

The Living Legacy of Landsat 7: Still Going Strong after 20 Years in Orbit (NASA)

 

Landsat 7 Spacecraft Facts

  • Power provided by a single Sun-tracking solar array and two 50 Ampere-Hour (AHr), Nickel Cadmium (NiCd) batteries
  • Attitude control provided through four reaction wheels (pitch, yaw, roll, and skew); three 2-channel gyros with celestial drift updating; a static Earth sensor; a 1750 processor; and torque rods and magnetometers for momentum uploading
  • Orbit control and backup momentum unloading provided through a blow-down monopropellant hydrazine system with a single tank containing 270 pounds of hydrazine, associated plumbing, and twelve 1-pound-thrust jets
  • Weight: approx. 4,800 lbs (2,200 kg)
  • Length: 4.3 m (14 ft)
  • Diameter: 2.8 m (9 ft)
  • Direct Downlink with Solid State Recorders (SSR)
  • Data rate: 150 Mbps

Landsat 7 Instrument

Landsat 7 carries the Enhanced Thematic Mapper Plus (ETM+) sensor, an improved version of the Thematic Mapper instruments that were onboard Landsat 4 and Landsat 5. Landsat 7 products are delivered as 8-bit images with 256 grey levels. Descriptions of Landsat 7 band designations and comparisons of all Landsat sensors are available.

Enhanced Thematic Mapper Plus (ETM+)

  • Eight spectral bands, including a pan and thermal band:
    • Band 1 Visible (0.45 - 0.52 µm) 30 m
    • Band 2 Visible (0.52 - 0.60 µm) 30 m
    • Band 3 Visible (0.63 - 0.69 µm) 30 m
    • Band 4 Near-Infrared (0.77 - 0.90 µm) 30 m
    • Band 5 Short-wave Infrared (1.55 - 1.75 µm) 30 m
    • Band 6 Thermal (10.40 - 12.50 µm) 60 m Low Gain / High Gain
    • Band 7 Mid-Infrared (2.08 - 2.35 µm) 30 m
    • Band 8 Panchromatic (PAN) (0.52 - 0.90 µm) 15 m
  • Ground Sampling Interval (pixel size): 30 m reflective, 60 m thermal
  • Added the Band 6 Low and High gain 60 m thermal bands
  • On-board calibration was added to Landsat 7: a Full Aperture Solar Calibrator (FASC) and a Partial Aperture Solar Calibrator (PASC), in addition to the 2 calibration lamps

Landsat 7 Data Products

Landsat 7 data products are consistent with all Landsat standard data products, using the specifications described on the Landsat Processing Details page.

Landsat 7 Scan Line Corrector (SLC) Failure

Illustration of the Landsat 7 Scan Line Corrector (SLC) Failure

Above: Illustration of the Landsat 7 Scan Line Corrector (SLC) Failure Below: Example of SLC-off scene. 

On May 31, 2003, the Scan Line Corrector (SLC), which compensates for the forward motion of the satellite, failed. Subsequent efforts to recover the SLC were not successful, and the failure is permanent. Without an operating SLC, the sensor’s line of sight traces a zig-zag pattern along the satellite ground track.

As a result, the imaged area is duplicated, with a width that increases toward the edge of the scene.  When the Level-1 data are processed, the duplicated areas are removed, leaving data gaps. Although these scenes only have 78 percent of their pixels remaining after the duplicated areas are removed, these data are still some of the most geometrically and radiometrically accurate of all civilian satellite data in the world.

A Landsat 7 SLC-off Scene Example

A number of papers were written about the Landsat 7 Scan Line Corrector: 

Landsat 7 End of Life Plans (View this USGS News Release)

On February 7, 2017, the twentieth and final inclination (Delta-I) maneuver of Landsat 7 took place. (Delta-I maneuvers keep the spacecraft in the correct orbital position to ensure it maintains its 10:00 am ± 15 minutes mean local time (MLT) equatorial crossing.)  Landsat 7 reached its peak outermost inclination boundary of 10:14:58 MLT on August 11, 2017.

The chart below illustrates the inclination trend from June 2014 to June 2026. By the end of 2021, the satellite will have a MLT of 9:00 am. 

Landsat 7 Satellite Orbital Inclination Timeframe

The USGS and NASA are planning for Landsat 7 to remain on-station and fulfilling its current science mission until Landsat 9 completes its launch (scheduled for September 16, 2021), on-orbit checkout, and commissioning. Sometime after Landsat 9 is nominally acquiring science mission data, Landsat 7 will exit the constellation and lower its orbit by 8 km to prepare for servicing by NASA’s On-Orbit Servicing, Assembly, and Manufacturing-1 (OSAM-1) mission. The mission - the first of its kind in low Earth orbit - will provide Landsat 7 with the needed fuel for a successful decommissioning.

 

Landsat 7 Data User's Handbook 

Landsat 7 Information (NASA Landsat Science)

Landsat 8/LDCM’s Underfly with Landsat 7: In March 2013, the Landsat 8 satellite (then known as LDCM) was in position under Landsat 7 to collect near-coincident data for calibration activities.