DARPA Space Telescope Will Track Objects in Geostationary Orbit

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WASHINGTON — A new ground-based telescope developed by the U.S. Defense Advanced Research Projects Agency (DARPA) is undergoing calibration and will soon enable wide-field views of objects in geostationary orbit, a Defense Department official said April 29.

After nine years of development, DARPA’s new Space Surveillance Telescope at White Sands Missile Range, N.M., began peering into deep space in February and has performed “remarkably well” so far, Air Force Lt. Col. Travis Blake, the program’s manager, said in an interview.

The Air Force is responsible for tracking satellites and other objects in Earth orbit and reporting that information to U.S. Strategic Command. The service utilizes a network of optical telescopes and radar sites around the world as well as space-based assets to maintain a catalog of more than 20,000 space objects.

Satellites and debris in low Earth orbit can be tracked with radar signals, but more distant objects are generally tracked with optical systems, such as the Air Force’s Ground-based Electro-Optical Deep Space Surveillance system (GEODSS) which tracks objects in geostationary orbit with telescopes in Maui, Hawaii; Socorro, N.M.; and the island of Diego Garcia in the Indian Ocean.

New technologies developed for the $110 million Space Surveillance Telescope will enable it to conduct faster and more accurate and sensitive searches than the GEODSS telescopes, Blake said. Massachusetts Institute of Technology’s Lincoln Laboratory in Lexington, Mass., developed the telescope’s digital imaging sensor and served as the prime integrator, while L-3 Brashear of Pittsburgh developed the optical components.

Since the Space Surveillance Telescope first began viewing the sky in February, the team has been steadily improving the accuracy of its images, Blake said. Once the calibration phase is complete, the system will begin a technology demonstration phase.

“We are still in alignment phase,” Blake said. “We have achieved first light but we have better performance to get out of the system.

“After we get the system to meet all of our specifications and it is at the best focus, we’re going to verify the sensitivity parameters, the search rate parameters that we designed into the system, as well as photometrics, and then go off and demonstrate all of the operational capabilities that we designed the sensor to do. Our goal right now is we are anticipating having that done by fall of this year.”

As a research and development organization, DARPA’s work with the telescope will end after the technology demonstration phase. Air Force Space Command intends to begin using the Space Surveillance Telescope later this year as a compliment to its other space surveillance assets, Air Force spokesman Andy Roake said in an April 29 email.

What makes the Space Surveillance Telescope unique is its aspheric mirror and curved charged coupled device sensor, Blake said. Most telescopes are designed with spherical mirrors that have a single radius of curvature throughout and flat charged coupled devices, the integrated circuits at the heart of digital imaging devices. These designs require additional optics to project an image of a curved field of view onto a flat sensor.

The aspheric mirror “allows the optical design to be more compact so we don’t have to use other refractive optics to create a flat field to be imaged onto a flat focal plane,” Blake said. “We’re able to take a curved field and image it onto a curved focal plane, which allows for a simpler, more compact design.”