CHAPTER 2 SECTIONS > Overview | Platform Details | Functions | Comm Links | Solid State Recorder

2.1 Overview

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 cycle. 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 sensor, 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.