Raumfahrt - NASA´s OPALS überträgt Daten von ISS per Laser


NASA's OPALS to Beam Data From Space Via Laser
PASADENA, Calif. -- NASA will use the International Space Station to test a new communications technology that could dramatically improve spacecraft communications, enhance commercial missions and strengthen transmission of scientific data.
The Optical Payload for Lasercomm Science (OPALS), an optical technology demonstration experiment, could improve NASA's data rates for communications with future spacecraft by a factor of 10 to 100. OPALS has arrived at NASA's Kennedy Space Center in Florida from the agency's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. It is scheduled to launch to the space station later this year aboard a SpaceX Dragon commercial resupply capsule on the company's Falcon 9 rocket.
"OPALS represents a tangible stepping stone for laser communications, and the International Space Station is a great platform for an experiment like this," said Michael Kokorowski, OPALS project manager at JPL. "Future operational laser communication systems will have the ability to transmit more data from spacecraft down to the ground than they currently do, mitigating a significant bottleneck for scientific investigations and commercial ventures."
OPALS will be mounted on the outside of the International Space Station and communicate with a ground station in Wrightwood, Calif., a mountain town near Los Angeles.
"It's like aiming a laser pointer continuously for two minutes at a dot the diameter of a human hair from 30 feet away while you're walking," explained OPALS systems engineer Bogdan Oaida of JPL.
The OPALS instrument was built at JPL and is slated to fly on the Dragon capsule in late 2013. The mission is expected to run 90 days after installation on the station.
The OPALS Project Office is based at JPL, a division of the California Institute of Technology in Pasadena.

Why Optical Communication?
The scientific instruments in near-Earth and deep-space missions increasingly require higher communication rates to transmit their gathered data back to Earth or to support high-data-rate applications (e.g., high-definition video streams). Optical communications (also referred to as 'lasercomm') is an emerging technology wherein data is modulated onto laser beams, which offers the promise of much higher data rates than what is achievable with radio-frequency (RF) transmissions.

The OPALS Project:
OPALS will demonstrate optical communication by transferring a video from our payload on the International Space Station (ISS) to our ground receiver at JPL's Optical Communications Telescope Laboratory (OCTL) in Wrightwood, California. As the ISS travels across the sky, a laser beacon will be transmitted from the ground telescope to our payload and tracked. While maintaining lock on the uplink beacon using a closed loop control system and a two-axis gimbal, the OPALS flight system will downlink a modulated laser beam with a formatted video. Each demonstration lasts for approximately 100 seconds as the ISS payload and ground telescope maintain line of sight.

OPALS Mission Architecture
OPALS Concept of Operations
System Description:
1. Flight System:
  The flight system is composed of three main elements:
    1. Sealed Container: houses all of the commercial-of-the-shelf (COTS) avionics boards, the laser, and custom power board pressured at 1 atmosphere with air. Connected to optical gimbal transceiver via cable feedthroughs.
    2. Optical gimbal transceiver: an optical head that contains an uplink camera and laser collimator for the downlink sits on a two-axis gimbal.
    3. Flight Releasable Attachment Mechanism (FRAM): both the sealed container and Optical gimbal transceiver sit on the FRAM, which provides a standard mechanical and electrical interface to both the ISS and the launch vehicle.
2. Ground System:
The OPALS ground system will be at the Optical Communications Telescope Laboratory (OCTL) at the JPL facilities on Table Mountain in Wrightwood, CA. It utilizes OCTL's 1-meter primary telescope aperture to receive the downlink signal and transmit the reference beacon. The received optical signal is acquired and focused onto a photodetector, which converts the optical signal to baseband electrical current. After necessary digitization, synchronization, error-correction and post-processing, the video file is displayed on a monitor. The OCTL telescope relies on orbital predicts generated by Johnson Space Center (JSC) to follow the ISS as it traverses its path across the sky.
3. International Space Station:
OPALS will be mounted externally on the International Space Station (ISS) in a nadir position on an ExPrESS Logistics Carrier (ELC).
4. Launch Vehicle:
OPALS is manifested to launch on the third ISS resupply mission by a SpaceX Falcon 9 Dragon in December 2013.
Quelle: NASA

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