Optical Communication and Sensor Demonstration (OCSD) - 10.25.17

Overview | Description | Applications | Operations | Results | Publications | Imagery

ISS Science for Everyone

Science Objectives for Everyone
Optical Communication and Sensor Demonstration (OCSD) tests specific functions of laser-based communications using automated CubeSats deployed from the International Space Station (ISS). Optical communication (communication using lasers) is a next generation technology that improves distance, accuracy and speed of communication in space and in space to ground applications. OCSD readies a compact version of this technology for space by demonstrating accurate high-speed optical communication between two small satellites working closely together in low-Earth orbit.
Science Results for Everyone
Information Pending

The following content was provided by Richard Welle, Ph.D., and is maintained in a database by the ISS Program Science Office.
Experiment Details

OpNom:

Principal Investigator(s)
Siegfried Janson, Ph.D., The Aerospace Corporation, Los Angeles, CA, United States
Richard Welle, Ph.D., The Aerospace Corporation, Los Angeles, CA, United States

Co-Investigator(s)/Collaborator(s)
Information Pending

Developer(s)
The Aerospace Corporation, Los Angeles, CA, United States

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
National Laboratory (NL)

Research Benefits
Earth Benefits

ISS Expedition Duration
September 2017 - February 2018

Expeditions Assigned
53/54

Previous Missions
Information Pending

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Experiment Description

Research Overview

  • Optical Communication and Sensor Demonstration (OCSD) sends optical communication with transmitters that are 100 times smaller than those previously flown.
  • Traditional laser communication systems use transmitters that are far too large for small spacecraft.
  • The high data rates, enabled by optical communication, open a number of new mission areas for next-generation small spacecraft.
  • The proximity operations mission demonstrates close maneuvering of very small spacecraft.
  • The propulsion system demonstrates the utility of simple, inexpensive, and safe propulsion for low-thrust close maneuvering.

Description

The Optical Communication and Sensor Demonstration (OCSD) project includes three 1.5-unit (1.5U) CubeSats launched on two separate missions. The first OCSD mission, with one satellite, launches aboard an Atlas rocket. This first OCSD flight is a risk reduction mission that allows inspection of the star trackers and important subsystems to include power, camera, GPS, radio and deployment mechanisms. The second OCSD mission includes two satellites. For the second mission, the laser communications system functions by transmitting data over the optical link to a ground station.
 
The optical communications system on OCSD differs from other space-based laser communication systems in that the laser is hard-mounted to the spacecraft body and the beam is pointed by controlling the orientation of the entire spacecraft. This makes the laser system much more compact. The attitude control system in these satellites includes a pair of miniature star trackers, which point to an accuracy of 0.05 degrees.
 
In addition to laser communications, the two satellites perform proximity operations, which involve maneuvering the two satellites relative to one another using variable drag and propulsion. The propulsion system on OCSD uses water as a propellant, and is exhausted as steam. Relative position measurements between the two satellites use cameras, beacons, and laser rangefinders.
 
The OCSD mission addresses the need for low-cost sensors that small spacecraft can use to assist in maneuvering and operating safely in close proximity to other spacecraft or objects in space. Capabilities in proximity operations enable multiple small spacecraft to: 1.) operate cooperatively during science or exploration missions, 2) approach another spacecraft or object for in-space observation or servicing, or 3) connect small spacecraft together to form larger systems or networks in space.

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Applications

Space Applications
OCSD benefits space exploration by preparing a critical technology for use in space. Understanding the performance of optical communication between small satellites, constrains the design of larger downlink systems that can dramatically expand the speed, range and quality of space to ground communications. These advances can increase the range and data gathering capabilities of space probes and help integrate operations among spacecraft of different sizes and in different configurations.

Earth Applications
Advances in communication technology such as those provided by OCSD contribute to remote sensing and mobile communication systems on Earth. Optical communications and optical networks specifically improve consumer products that use GPS or other satellite networks. Better networks provide better data, which generally benefits the military, the tech industry and meteorological agencies.

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Operations

Operational Requirements and Protocols

NanoRacks CubeSats are delivered to the ISS already integrated within a NanoRacks CubeSat Deployer (NRCSD) or NanoRacks DoubleWide Deployer (NRDD). A crew member transfers each NRCSD/NRDD from the launch vehicle to the Japanese Experiment Module (JEM). Visual inspection for damage to each NRCSD is performed. When CubeSat deployment operations begin, the NRCSD/NRDDs are unpacked, mounted on the JAXA Multi-Purpose Experiment Platform (MPEP) and placed on the JEM airlock slide table for transfer outside the ISS. A crew member operates the JEM Remote Manipulating System (JRMS) – to grapple and position for deployment. CubeSats are deployed when JAXA ground controllers command a specific NRCSD.
 
After ejection from the deployer, it takes three weeks to complete a thorough checkout of each spacecraft, including verification of all spacecraft systems, and calibration of all onboard sensors. Optical downlink testing begins after satellite checkout is complete. Each optical downlink test involves a series of steps, including: 1) collecting GPS data over several orbits for precision orbit determination, 2) forecasting the orbit trajectory over the optical ground station (OGS) and calculating the pointing requirements, 3) stabilizing the spacecraft and pointing system ahead of the pass 4) tracking the satellite with the OGS as it passes overhead, 5) pointing the satellite at the OGS and transmitting data, 6) receiving the data at the OGS, and 7) analyzing the data to evaluate transmitter performance. The optical mission involves a number of downlink tests under varying conditions (range, elevation angle, lighting conditions, and atmospheric variability) to evaluate performance.
 
The proximity operations start with two spacecraft separated by some kilometers, and the process starts with a series of variable drag maneuvers designed to bring the spacecraft within 2 km of one another. Variable drag works by changing the orientation of the spacecraft relative to the flight vector to increase or decrease the drag. If one satellite is in a slightly lower orbit than the other, the drag on the higher spacecraft is increased and decreased on the lower spacecraft to bring them into the same orbit. If one spacecraft is ahead of the other in the same orbit, drag is increased on the trailing spacecraft to cause it to fall into a lower orbit (where it moves faster than the spacecraft in the higher orbit). When the trailing spacecraft catches up to the leading spacecraft, the drag is increased on the leading spacecraft to cause it to fall into the same orbit as the trailing spacecraft.
 
After the variable drag sequence, both spacecraft are within 2 km of one another and propulsive orbit modifications are used to bring them within 200 m. The propulsion system uses heated water (steam) ejection through a nozzle to provide moderate thrust. Basic navigation of the two spacecraft uses GPS, but in proximity operations, the relative separation of the two spacecraft is measured using a laser rangefinder and a camera system that observes optical beacons on the partner spacecraft.
 
The two spacecraft are used continually for further refinement of the techniques for small-satellite laser communication.

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Decadal Survey Recommendations

Information Pending

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Results/More Information

Information Pending

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Related Websites
Optical Communications and Sensor Demonstration (OCSD)

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Imagery