Astronomers at MIT played a key role this week in identifying a near-Earth object as most likely the third stage of an Apollo-era moon rocket.
Based on an analysis of the orbital trajectory of the object, it appears that the object is the S-IVB stage from the Apollo 12 mission, launched to the moon on Nov. 14, 1969. Further analysis by NASA's Jet Propulsion Laboratory scientists indicates that the object is likely to complete six orbits of the Earth and then return to an orbit around the Sun sometime next summer.
Professor Richard P. Binzel and research scientist Andrew Rivkin from MIT's Department of Earth, Atmospheric and Planetary Sciences became aware of the discovery of the unusual object in Earth orbit earlier this month.
Amateur astronomer Bill Yeung discovered the object, known as J002E3, on Sept. 3. Paul Chodas of the Jet Propulsion Laboratory analyzed the object's orbit and determined that it entered an Earth-centric orbit in April after being in a heliocentric orbit.
"We had read about J002E3 and the question of whether it was an asteroid or Apollo Saturn stage, and realized that we had the chance to take an infrared spectrum and possibly help identify it," Rivkin said.
Binzel and Rivkin used NASA's Infrared Telescope Facility in Hawaii to conduct a spectral analysis of the object in infrared wavelengths of light between 0.8 microns and 2.5 microns. The telescope was operated remotely from a computer facility in the Green Building on the MIT campus.
Rivkin and Binzel analyzed the data to obtain a spectrum, and found it looked unlike any asteroids they had previously seen. While puzzling over the first night's data, they received an e-mail from Carl Hergenrother and Rob Whiteley, astronomers at the Lunar and Planetary Laboratory at the University of Arizona, who had also observed J002E3 in visible light using the Steward Observatory in the Santa Catalina Mountains.
"We were able to combine our two data sets and produce a single spectrum spanning the visible and infrared, which is of a shape that looks a lot like titanium oxide paint," Rivkin said. The third stage of the Saturn V moon rocket was painted with white titanium oxide paint.
Binzel and Rivkin were able to correlate the spectral analysis observed using the telescope with known measurements of titanium oxide paint. "We now have available titanium oxide paint measurements at near-infrared wavelengths that are an excellent match to the telescopic measurements using NASA's Infrared Telescope Facility," said Professor Binzel, whose work is partially funded by the National Science Foundation.
The Saturn V's third stage, called the S-IVB, was used in the Apollo program to perform the Trans Lunar Injection burn, which increased the Apollo spacecraft's velocity to 25,000 miles per hour on a trajectory to the moon. On the first four lunar missions (Apollo 8, 10, 11 and 12), the S-IVB was left in a heliocentric orbit. Beginning with Apollo 13 in 1970, the spent third stages were targeted at the moon so that scientists could measure the lunar impact with seismometers that were deployed as part of the Apollo lunar surface experiments package.