The George R. Wallace, Jr., Astrophysical Observatory is a teaching and research observatory located in Westford, Massachusetts. Its facilities consist of a 24-inch telescope, a 16-inch telescope, several 14- and 8-inch telescopes, a 5.5-inch astrograph, and a building that houses a workshop, darkroom, computer facility, and observers' quarters. Instruments used during the past year include the SNAPSHOT high-speed dual-CCD photometer, a portable high-speed CCD occultation system, several small CCD systems, conventional photometers, photographic cameras, and a high-resolution spectrograph. Work is continuing to improve the optics of the 24-inch telescope, and a low-resolution spectrograph is being studied for the smaller telescopes.
Professor James L. Elliot continued his duties as Observatory Director. Principal Research Scientist Heidi B. Hammel assisted with site management and telescope scheduling, with the help of Research Specialist Rich Meserole. Mr. Michael Person has replaced Mr. Michael Mattei as a part-time Technical Assistant for making observations, helping with observatory maintenance, and training students. Other staff (usually students) is coordinated through research programs. An undergraduate working on the spectrograph project (Asantha Cooray) is participating in the Undergraduate Research Opportunities Program (UROP); other students (Vincent Fish, Lisa Kwok, Lucy Lim, and Angela Hancock) are supported in part by NSF's Research Experiences for Undergraduates.
Last year, course 8.287J-12.410J (Observational Techniques of Optical Astronomy) drew 11 students, who used the Wallace facilities for a variety of astronomical projects. An additional 22 students in subject 12S23 (Observing the Stars and Planets) used the Observatory for laboratory work. Informal field trips were offered for courses 12.401 (Beyond the Solar System; 17 students) and 12S22 (Hands-on Astronomy; 14 students), as was an observing session for freshmen last fall. An open house held during MIT's 1996 Independent Activities Period attracted over 40 people (mostly undergraduates, though faculty and staff from other departments came). The MIT SEDS Club (Students for the Exploration and Development of Space) also hosted an undergraduate evening for observing in October 1995, which drew about 30 students.
Mr. McDonald, graduate student Jeff Foust, and Mr. Mattei used the 24-inch to obtain astrometric CCD data for Pluto and the star P28 (which Pluto nearly occulted in July 1995), Neptune's moon Triton and the star Tr148 (which Triton occulted in August 1995), and Saturn's moon Titan and the star GSC5254-00997 (which Titan occulted in August 1995). Graduate student Cathy Olkin, Dr. Hammel, Professor Elliot, Mr. Cooray, and colleagues successfully observed the Triton event with both NASA's Kuiper Airborne Observatory and the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. The data, analyzed and modeled as part of Ms. Olkin's successful doctoral dissertation, revealed an unexpected lack of a temperature gradient in Triton's lower atmosphere. The Titan event was observed on the NASA IRTF; graduate student Philip Tracadas is analyzing those data.
Mr. Foust used observations of Pluto and its moon Charon made with the 24-inch to determine the mass ratio of Pluto and Charon. The number has been in contention since two conflicting reports appeared, based on data from the Hubble Space Telescope in 1993 and the University of Hawaii 2.2-m telescope in 1994. Mr. Foust's value from Wallace (0.121 +/- 0.006) supports a newer estimate made with HST reported in 1996 (0.124 +/- 0.008).
Dr. Steve Slivan used the 24-inch to observe rotational lightcurves of the asteroid Eriphyla. Dr. Slivan developed an extensive database of asteroid photometry using Wallace facilities as part of his successful MIT doctoral dissertation. Dr. Slivan also continued a project of imaging objects from the Messier Catalog.
Mr. McDonald and students also used CCD data from the 24-inch to continue astrometric and photometric observations of occultation candidate stars for future events involving Saturn, Uranus, Pluto, and Triton, and Mr. Foust conducted a search for stars that may be occulted by several comets. Astrometric and photometric observations continued in support of the Hubble Space Telescope, with Dr. Amanda Bosh (Lowell Observatory) assisting in coordination of that effort.
Heidi B. Hammel