Table Mountain Observatory, usually abbreviated TMO, is the astronomical portion of NASA JPL’s Table Mountain Facility above Wrightwood in the San Gabriel Mountains. The larger Table Mountain Facility is a 37-acre research site overlooking the Mojave Desert, about 60 miles northeast of JPL’s Pasadena campus, at roughly 7,300 feet elevation. JPL notes that the altitude, mountain barrier, and distance from Los Angeles air pollution make the site unusually good for observing and atmospheric measurements.
The site has an older scientific history than many people realize. The Smithsonian Institution established the observatory in 1926 for solar irradiance studies. JPL had been using the mountain for spacecraft solar-panel testing by the late 1950s and early 1960s, then acquired the U.S. Forest Service lease in 1962. That same year, JPL built TM-1, installed a 16-inch optical telescope, and recorded first light on August 1, 1962.
TMO is not only an astronomy site. Table Mountain Facility has supported solar testing, spacecraft-related calibration, atmospheric lidar, ozone and water-vapor measurements, and instrument intercomparison campaigns. JPL’s lidar group describes the site as valuable because of its remote location, altitude, climate, and dark sky conditions. Long-term lidar work there has measured stratospheric ozone, temperature, aerosols, tropospheric ozone, and water vapor.
One important modern telescope at TMO is Pomona College’s 1-meter, 40-inch telescope, shared with JPL. Pomona says the telescope has a 40.5-inch mirror, f/9.5 effective focal ratio, CCD imaging, filter wheels, polarimetry capability, near-infrared instrumentation, and adaptive optics. The telescope was built in the 1982-1985 period, received new optics in the 1990s, and later became useful for student and research observing.
For a Mojave or Wrightwood page, the key point is this: Table Mountain Observatory is a mountain-edge science station where the San Gabriels meet the desert sky. It belongs to the same regional story as Cajon Pass, Big Pines, Angeles Crest, Wrightwood, and the Mojave overlook country, but its purpose is scientific rather than recreational.
Additional reading: JPL Table Mountain Facility history, JPL Table Mountain lidar site, NDACC Table Mountain Facility station page, and Pomona College’s Table Mountain Observatory page.