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Optical PAyload for Lasercomm Science (OPALS)

opals

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 Mission Architecture



OPALS Concept of Operations
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.

OPALS Flight System

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.

Ground System

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). The OPALS instrument is scheduled to begin commissioning activities, onboard the ISS, in May of 2014.

International Space Station

4. Launch Vehicle:
OPALS launched on an ISS resupply mission in the trunk of the SpaceX Falcon 9 Dragon capsule on April 18, 2014.

5. Publications:
Oaida, B., Abrahamson, M., Witoff, J., Bowles-Martinez, J., and Zayas, D., "OPALS: An Optical Communications Technology Demonstration from the International Space Station," Aerospace Conference, IEEE, Big Sky, MT, 2-9 March 2013.

Oaida, B., Wu, W., Erkmen, B., Biswas, A., Andrews, K., Kokorowski, K., and Wilkerson, M., "Optical Link Design and Validation Testing of the Optical Payload for Lasercomm Science (OPALS) System," Proc. SPIE 8971, Free-Space Laser Communication and Atmospheric Propagation XXVI, 897131, February 2014.

For additional information, contact Michael Kokorowski: Michael.Kokorowski@jpl.nasa.gov or go to http://www.nasa.gov/mission_pages/station/research/experiments/861.html