AFRL telescope spots asteroid's moon

  • Published
  • By Jeanne Dailey
  • Air Force Research Laboratory
KIRTLAND AIR FORCE BASE, N.M. --   In a first for the Air Force, scientists at the Air Force Research Laboratory's Starfire Optical Range used its 3.5-meter telescope and adaptive optics with a laser guidestar to capture the image of a moon named Romulus around the asteroid Sylvia. 

The telescope, which measures 3.5-meter (11.5 feet) in diameter, is the smallest ground-based telescope ever to image any asteroid satellite. Since Sylvia is too faint for normal adaptive optics, AFRL sent a laser into the atmosphere to create an artificial guidestar for this research. Sylvia measures 175 kilometers in diameter.

"Previous images have all been made with an 8- or 10-meter telescope and one was obtained with the Hubble Space Telescope from space," said AFRL's Directed Energy Directorate scientist Jack Drummond.  "The ability to detect a moon around an asteroid closely mimics a small satellite approaching a larger satellite in geosynchronous orbit -- a main area of concern for the Air Force in protecting our nation's space assets."

Thirty kilometers in diameter, Romulus is one of two known moons that orbit around the asteroid that lies between Mars and Jupiter.  Romulus is 80 times fainter than its parent Sylvia, which at V magnitude 12.5 is about the brightness of a geosynchronous satellite, and some 250 times fainter than the dimmest star visible to the naked eye.

AFRL's Starfire Optical Range is a world-class optical research facility and center for Air Force optical exploration.  It is located on a hilltop site 6,240 feet above sea level on Kirtland Air Force Base, N.M.

"As satellites get smaller and the number of space objects increases dramatically, research in imaging and identification of space objects becomes paramount to the Air Force's mission," Drummond said.  "Using adaptive optics, the 3.5-meter telescope is able to distinguish basketball-sized objects at a distance of 1,000 miles into space."

The premier adaptive optics telescope is the second largest telescope in the Department of Defense. It was installed at the SOR in August 1993 and the mirror received "first light" images on Feb. 10, 1994.  One of its unique features is that the 4,500 pound primary mirror is protected by a retracting cylindrical enclosure that allows the telescope to operate in the open air. 

"Operating the telescope in the open air provides a couple of advantages over conventional domes," Drummond said.  "We can track satellites without rotating the dome at high speeds, and we receive higher quality images due to the release of warmer trapped air that could cause optical distortions."

He said the next step in this research will be to see how small a moon scientists can detect around an asteroid using the laser guide star system. 

"There are a handful of asteroids with moons that we can image, but we cannot conduct similar experiments on geosynchronous satellites because we are not allowed to point a laser at man-made satellites," Drummond said.