12 foot diameter. balloon; atmospheric density studies.

Typical orbit: 757 km x 2433 km at 39 degrees inclination. Mass: 6.50 kg (14.30 lb). Associated Launch Vehicle: Scout X-1.

• 1960 December 4 - Explorer (9) S 56 - Program: Explorer. Launch Site: Wallops Island. Launch Vehicle: Scout X-1. FAILURE: Second stage malfunction. Mass: 6.00 kg (13.20 lb).

• 1961 February 16 - Explorer 9 - Program: Explorer. Launch Site: Wallops Island. Launch Vehicle: Scout X-1. Mass: 7.00 kg (15.40 lb). Perigee: 757 km (470 mi). Apogee: 2,433 km (1,511 mi). Inclination: 38.80 deg. Period: 118.00 min.

  12 foot dia. balloon; atmospheric density studies. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B).

• NASA Report, Determination of Mean Atmospheric Densities from the Explorer IX Satellite, . Accessed at: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19650018214_1965018214.pdf. -right click to download pdfs!

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

• 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.

• Bramscher, Robert G, Spaceflight, "A Survey of Launch Vehicle Failures", 1980, Volume 22, page 351.

• NASA Report, Temperature Control of the Explorer IX Satellite , . Accessed at: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19620003946_1962003946.pdf. -right click to download pdfs!