Space craft engaged in investigation of spaceflight techniques and technology. The Rigidsphere and Gridsphere satellites of the 1960s were wire frames, embedded in an inflatable plastic substrate that sublimated away in space, leaving the open wire grid spheres.

Typical orbit: 781 km x 916 km at 88 degrees inclination. Mass: 6.00 kg (13.20 lb). Associated Launch Vehicle: Atlas F.

• 1971 August 7 - Rigidsphere - Launch Site: Vandenberg. Launch Vehicle: Atlas F. Mass: 6.00 kg (13.20 lb). Perigee: 781 km (485 mi). Apogee: 916 km (569 mi). Inclination: 87.60 deg. Period: 101.80 min.

  Space craft engaged in investigation of spaceflight techniques and technology (US Cat A).

• McDowell, Jonathan, Jonathan's Space Home Page, Harvard University, 1997-present. Jonathan McDowell's complete on-line listing of all objects orbited and over 20,000 rocket launches Accessed at: http://www.planet4589.org/jsr.html.

• Krebs, Gunter, Gunter's Space Page, University of Frankfurt, 1996. Accessed at: http://www.skyrocket.de/space.

• JPL Mission and Spacecraft Library, Jet Propulsion Laboratory, 1997. Accessed at: http://msl.jpl.nasa.gov/home.html.

• Lockheed Martin Coporation, Atlas Family Fact Sheets, September 1998.. Accessed at: http://www.lmco.com/ILS/txtmain/ils_lsysinfo.htm.

• McDowell, Jonathan, Launch Log, October 1998. Jonathan McDowell's complete on-line listing of all objects orbited since Sputnik. Accessed at: http://hea-www.harvard.edu/~jcm/space/log/launch.html.

• USAF Satellite Database, USAF Institute of Technology, 1995. Accessed at: ftp://archive.afit.af.mil/pub/space/.