Landsat 7

Involving three large American governmental organizations: NASA, NOAA and USGS launched on April 15, 1999. Landsat 7 is equipped with ETM+ (Enhanced Thematic Mapper Plus), which provides a ground survey in four modes: VNIR (Visible and Near Infrared), SWIR (Shortwave Infrared), PAN (Panchromatic – Panchromatic range), TIR (Thermal infrared – Thermal infrared range).

The Landsat 7 ETM+ instrument is designed with the significant exception of the thermal infrared band, where the ground resolution has been improved from 120 to 60 m.

The ETM instrument incorporates a new 15 m panchromatic band, as well as a 9-bit analog to digital converter. The panchromatic band was added to provide higher spatial landsat 7 resolution observations, as a compliment to the 30 m multispectral measurements. In order to limit the telemetered data stream to a reasonable volume, a 9-bit A-to-D system was designed so that either the upper or lower 8 bits of the radiometry could be provided from the system. This introduces the potential for two gain states (high and low), which, particularly for dark landscapes, could increase the radiometric signal.

At an altitude of 705 km, a full surface scan by Landsat 7 takes 232 turns, or 16 days. The terrain survey takes place at approximately 10 am (± 15 minutes) according to local solar time.

Landsat 7 Characteristics
Characteristic	Description
Participants	NASA NOAA DOI USGS Spacecraft bus Enhanced Thematic Mapper Plus
Launch Date	April 15, 1999
Vehicle	Delta II
Site	Western Test Range at Vandenberg Air Force Base, California
Spacecraft	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)
Communications	Direct Downlink with Solid State Recorders (SSR) Data rate: 150 Mbps
Orbit	Worldwide Reference System-2 (WRS-2) path/row system Sun-synchronous orbit at an altitude of 705 km (438 mi) 233 orbit cycle; covers the entire globe every 16 days (except for the highest polar latitudes) Inclined 98.2° (slightly retrograde) Circles the Earth every 98.9 minutes Equatorial crossing time: 10:00 a.m. +/- 15 minutes
Sensors	ETM+
Scene size	170 km x 185 km (106 mi x 115 mi)
Design life	Minimum of 5 years

Landsat 7 Bands
Sensor	Band number	Band name	Wavelength (μm)	Resolution (m)	Band Applications
ETM+	Band number1	Band nameBlue	Wavelength (μm)0.45-0.52	Resolution (m)30	Band ApplicationsBathymetric mapping, distinguishing soil from vegetation, and deciduous from coniferous vegetation
ETM+	Band number2	Band nameGreen	Wavelength (μm)0.52-0.60	Resolution (m)30	Band ApplicationsEmphasizes peak vegetation, which is useful for assessing plant vigor
ETM+	Band number3	Band nameRed	Wavelength (μm)0.63-0.69	Resolution (m)30	Band ApplicationsDiscriminates vegetation slopes
ETM+	Band number4	Band nameNIR	Wavelength (μm)0.77-0.90	Resolution (m)30	Band ApplicationsEmphasizes biomass content and shorelines
ETM+	Band number5	Band nameSWIR 1	Wavelength (μm)1.55-1.75	Resolution (m)30	Band ApplicationsDiscriminates moisture content of soil and vegetation; penetrates thin clouds
ETM+	Band number6	Band nameThermal	Wavelength (μm)10.40-12.50	Resolution (m)60*(30)	Band ApplicationsThermal mapping and estimated soil moisture
ETM+	Band number7	Band nameSWIR 2	Wavelength (μm)2.09-2.35	Resolution (m)30	Band ApplicationsHydrothermally altered rocks associated with mineral deposits
ETM+	Band number8	Band namePanchromatic	Wavelength (μm)0.52-0.90	Resolution (m)15	Band Applications15 meter resolution, sharper image definition

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