The Optical Communications and Sensor Demonstration (OCSD) mission will address two crosscutting capabilities of interest to NASA: optical communications system and low-cost sensors for proximity operations with cubesats and other spacecraft. The OCSD project is led by the Aerospace Corporation, in El Segundo, California and is funded by NASA’s Small Spacecraft Technology Program.
The spacecraft for this mission will be two 1.5-unit cubesats, which are satellites with dimensions of approximately 10 by 10 by 16 centimeters and a mass of approximately 3 kilograms. This two-year project was initiated in October 2012.
With its first objective, this project addresses the need to increase the amount of data that a small spacecraft can transmit to the ground. For a given amount of communications system power, optical systems, that transmit information using a laser beam rather than a radio signal, offer the potential to greatly increase the volume of information that can be transmitted by a spacecraft. Optical communications systems are of interest for use in spacecraft of any size and this project provides an opportunity to advance this technology quickly and at very low cost.
The communications concept that will be demonstrated is an asymmetric one in which the satellite uses an laser beam to transmit large amounts of data to the ground while it uses a conventional radio-frequency system to receive commands from the ground. This system would be beneficial for small-satellite missions that need to transmit large amounts of data but have very limited power available onboard.
The second objective of the project addresses the need for low-cost sensors that small spacecraft can use to help them maneuver and operate safely in close proximity to other spacecraft or objects in space. Capabilities in proximity operations will enable multiple small spacecraft to operate cooperatively in science or exploration missions, to approach another spacecraft or object in space for observation or servicing, or to connect small spacecraft together to form larger systems in space.
A small radar system adapted from the automotive industry will be used to determine the distance between the satellites at close range. A laser device on each satellite, derived from the system used in a computer mouse, will be used to measure the cross-track motion of the partner satellite, or other objects. Spacecraft that need to operate in close proximity to other spacecraft could make use of these low-cost sensors to keep track of the position and motions of other nearby spacecraft or objects. This project is a good example of applying the technology of everyday commercial products to new uses in spacecraft.
To accomplish the mission, the two 1.5U cubesats will be deployed from a standard cubesat dispenser and placed into a circular or near-circular orbit. The desired orbit is one with an average altitude no higher than 550 kilometers and an orbital inclination of at least 34 degrees.
To demonstrate the proximity operations sensors, the two cubesats will maneuver to within 200 meters of each other using on-board GPS to determine their position and velocity. The spacecraft will be able to change their positions using a combination of cold gas thrusters for propulsion and an innovative approach of varying the cross-sectional area of the spacecraft, and thereby its aerodynamic drag, by opening and closing its hinged solar panels. While they are in close proximity, the spacecraft will demonstrate the inexpensive radar units for determining range between the satellites and the optical flow sensors for cross-track motion detection.
Demonstration of the space-to-ground optical communications link will be performed with a ground based optical tracking system using commercial 30-centimeter (12-inch) telescopes controlled by custom-built high-accuracy pointing systems.
The OCSD project was selected for a flight opportunity by NASA’s Cubesat Launch Initiative. OCSD’s two spacecraft will be launched on a rideshare mission arranged by the Launch Services Program at NASA’s Kennedy Space Center. The spacecraft will be ready for launch by 2015.