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Optical PAyload for Lasercomm Science (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 successfully demonstrated optical communication by transferring videos and files from the nadir-pointed payload on the International Space Station (ISS) to our primary ground receiver at JPL's Optical Communications Telescope Laboratory (OCTL) in Wrightwood, California, and at times, other international ground stations. As the ISS travels across the sky, a laser beacon is transmitted from the ground telescope to our payload for closed-loop tracking. While maintaining lock on the uplink beacon using a closed loop control system and a two-axis gimbal, the OPALS flight system has downlink a modulated laser beam with a formatted video or other types of file (e.g., text). Each demonstration lasts for approximately 150 seconds as the ISS payload and ground telescope maintain line-of-sight.
OPALS Mission Architecture
OPALS Concept of Operations
System Description:
| 1. Flight System: |
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The flight system is composed of three main elements:
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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. |
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Optical gimbal transceiver: an optical head that contains an uplink camera and laser collimator for the downlink sits on a two-axis gimbal. |
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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: |
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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 predictions built from ISS GPS state vectors to follow the ISS as it traverses its path across the sky. |
OPALS has also attempted optical laser communications with other ground stations: ESA's optical ground station (OGS) in Tenerife and DLR's ground station in Oberpfaffenhofen.
| 3. International Space Station: |
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OPALS instrument was mounted externally on the International Space Station (ISS) in a nadir position on an ExPrESS Logistics Carrier 1 (ELC-1) on May 7, 2014.
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OPALS instrument installation on ISS ELC-1 on May 7, 2014 |
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Close up of installed OPALS instrument on ELC-1 on May 7, 2014 |
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The OPALS instrument begin commissioning activities, onboard the ISS, on May 10, 2014. |
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Moonrise over the OPALS instrument during commissioning activities on May 14, 2014 |
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OPALS instrument prior to a closed looping tracking of a ground beacon commissioning activity on May 25, 2014 |
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OPALS instrument firing a laser |
| 4. Launch Vehicle: |
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OPALS launched on an ISS resupply mission in the trunk of the SpaceX Falcon 9 Dragon capsule on April 18, 2014. |
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OPALS instrument inside SpaceX's Dragon's trunk, after second stage launch vehicle separation, on April 18, 2014 |
| 5. OPALS Videos (Animation: Canadian Space Agency) |
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The link below is a computer-generated animation shows Dextre, the Canadian robotic handyman on board the International Space Station (ISS),
retrieving OPALS from inside the trunk of SpaceX's Dragon cargo ship, and installing it on the exterior of the ISS.
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| Dextre installs OPALS on the International Space Station.: |
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This tracking video was recorded at the Optical Communications Telescope Laboratory (OCTL) at the JPL Table Mountain Facility (TMF) in Wrightwood, CA on the morning of April 3, 2013 between the hours of 5:53am and 5:59am local time. This video shows the view through the 500-urad wide main scope at the OCTL telescope throughout the 6-minute pass over Los Angeles, ranging from a distance of 1200km at the approaching horizon at 5:53am, to a closest approach of 422 km at 5:55:43am, to a distance of nearly 1500km at the departing horizon at 5:59am. The ISS approached from the northwest, to the west of San Francisco, and departed to the southeast, just to the east of Baja California. At closest approach, the ISS was approximately 72 degrees above the horizon.
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Tracking video recorded at the Optical Communications Telescope Laboratory (OCTL) |
| 6. References: |
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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.
Abrahamson, M., Sindiy, O., Oaida, B., Fregoso, S., Bowles-Martinez, J., Kokorowski, M., Wilkerson, W., and Konyha, A., "OPALS: Mission System Operations Architecture for an Optical Communications Demonstration on the ISS," SpaceOps 2014 13th International Conference on Space Operations, Pasadena, CA, 5-9 May 2014. AIAA-2014-1627."
Abrahamson, M., Oaida, B., Sindiy, O., Biswas, A., "Achieving Operational Two-way Laser Acquisition for OPALS Payload on the International Space Station," SPIE Photonics West, San Francisco, CA, 7-12 Feb. 2015.
Wright, M., Wilkerson, M., Tang, R., "Qualification Testing of Fiber Based Laser Transmitters and On-orbit Validation of a Commercial Laser System," ICSO, Tenerife, Canary Islands, Spain, 7-10 Oct. 2014.
Wright, M., Morris, J., Kovalik, J., Andrews, K., Abrahamson M., Biswas, A., "LEO to Ground OPALS Optical Communication Link Using Adaptive Optics Correction into SMF," Optics Express, [to be published].
Selinger, M., "Demonstrating Laser Comms," AIAA Aerospace America, Sept. 2014.
Hsu J., "Space Station Laser Beams Video Message to Earth," IEEE Spectrum, 12 June 2014.
JPL Press Release: NASA Beams 'Hello, World!' Video from Space via Laser.
JPL Press Release, 9 Dec. 2014: OPALS: Light Beams Let Data Rates Soar
JPL Press Release, 14 May 2015: OPALS Boosts Space-to-Ground Optical Communications Research
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For additional information, contact Matthew Abrahamson: Matthew.Abrahamson@jpl.nasa.gov
or go to http://www.nasa.gov/mission_pages/station/research/experiments/861.html
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