CHAPTER 2 SECTIONS > Overview | Platform Details | Functions | Comm Links | Solid State Recorder
The Landsat 7 Handbook is out of date. A revised
version to bring the information up to date will be developed and posted
when complete. Please see the USGS Landsat site at
https://lta.cr.usgs.gov/LETMP for current information on Landsat 7 ETM+
data and data products.
Figure 2.1 Landsat 7 Launch
The Landsat 7 satellite was successfully launched from Vandenburg Air
Force Base on April 15, 1999. The Delta
II launch vehicle left the pad at 11:32 PDT and performed flawlessly.
The injected spacecraft, depicted in Figure 2.2 and in this
1.8 MB Quicktime movie, is a 5000 pound-class satellite designed
for a 705 km, sun synchronous, earth mapping orbit with a 16-day repeat
Its payload is a single nadir-pointing instrument, the Enhanced Thematic
Mapper Plus (ETM+). S-Band is used for commanding and housekeeping telemetry
operations while X-Band is used for instrument data downlink. A 378 gigabit
Solid State Recorder (SSR) can hold 42 minutes of instrument data and
29 hours of housekeeping telemetry concurrently. Power is provided by
a single Sun-tracking solar array (four 74" by 89.3" panels
- 184 square feet) and two 50 amp-hour Nickel-Hydrogen batteries. Attitude
control is provided through four reaction wheels (pitch, yaw, roll, skewed),
three 2-channel gyros with celestial drift updating, a static Earth
1750A processor, and torque rods and magnetometers for momentum unloading.
Orbit control and backup momentum unloading is provided through a blow-down
monopropellant hydrazine system with a single tank containing 270 pounds
of hydrazine, associated plumbing, and 12 one pound-thrust jets. Spacecraft
weight is approximately 4632 pounds at launch.