Technologies for Proximity Operations and Data Transmission

Optical Communications and Sensor 

Demonstration

In low-Earth-orbit since early December 

2017, the Optical Communications and 

Sensor Demonstration (OCSD) mission is 

addressing two cross-cutting capabilities 

of value to many future small spacecraft 

missions: high-speed optical transmission 

of data and small spacecraft proximity 

operations. The OCSD project is developing 

and leveraging technologies that consist of 

a low power laser communication system, 

proximity sensors, and a compact waterbased propulsion system to enable the 

demonstration of technology firsts in these 

two areas.

The OCSD project consists of three 1.5-unit 

(1.5U) CubeSats launched as secondary 

payloads on two separate missions. Each 

CubeSat is about 4 inches x 4 inches x 6.7 

inches (10 centimeters x 10 centimeters x 

17 centimeters) and weighs approximately 

5 pounds (2.5 kilograms). The first OCSD 

mission, with one satellite, launched on 

Oct. 8, 2015 aboard an Atlas V rocket from 

Vandenberg Air Force Base in California. 

This first OCSD flight was a risk-reduction 

mission that allowed some checkout of the 

star trackers and important subsystems 

including power, camera, GPS, radio, and 

deployment mechanisms. It also allowed 

calibration and tool refinements to support 

the operational second flight of OCSD.

The second OCSD mission, with two 

satellites, launched November 12, 2017 

on the Cygnus Resupply Mission (OA-8) 

from the Mid-Atlantic Regional Spaceport, 

Wallops Flight Facility, Virginia. Modified to 

incorporate the lessons learned during the 

first mission, the two satellites entered the 

operational phase of the mission in April to 

demonstrate the first-ever high-speed laser 

communication from a CubeSat to a ground 

station, as well as to demonstrate an optical 

communications uplink to a CubeSat for 

the first time. To date, laser alignment 

measurements are complete, and optical 

signals modulated at 100 megabits per 

second (Mb/s) have been received on the 

ground. Continuing work will involve higher 

data rates and detailed measurements of 

bit error rates. 

The proximity sensors developed for 

this mission to enable relative position 

measurement between the two small 

satellites will perform a capability not 

previously demonstrated. The proximity 

operations demonstration will involve 

relative position measurements using 

cameras, beacons, laser rangefinders, 

and relative maneuvering using variable 

drag and a water-based propulsion system 

on board each spacecraft. To date, the 

thrusters have been used to maneuver 

the two satellites to within 20 feet of one 

another. Later this summer, the spacecraft 

will execute more complex maneuvers and 

demonstrate the operation of the proximity 

sensors.

The optical communications system on 

OCSD differs from other space-based laser 

communication systems because the laser 

is hard-mounted to the spacecraft body. 

One of two Optical Communications and 

Sensor Demonstration (OCSD) spacecraft 

being processed for payload integration.

Credit: NanoRacks.
The beam is pointed by controlling the orientation of 

the entire spacecraft. This makes the laser system 

much more compact than anything previously flown in 

space. The attitude control system developed for these 

satellites includes a pair of miniature star trackers, 

which are cameras that measure the position of stars 

for navigational purposes. The attitude-control system 

of the OCSD spacecraft, using these star trackers, 

has demonstrated pointing with an accuracy better 

than 0.05 degrees, which is 20 times the precision 

previously demonstrated in a satellite of this size.

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 will enable multiple small 

spacecraft to operate cooperatively during science or 

exploration missions, to approach another spacecraft 

or object for in-space observation or servicing, or 

to connect small spacecraft together to form larger 

systems or networks in space.

The potential for optical communications technology 

will not reach its limit with OCSD; it is anticipated that 

relatively simple upgrades, primarily to the attitude 

control system, will enable download rates of 2.5 

gigabits per second (Gb/s) or higher. This would open 

the possibility of using small satellites in applications, 

such as synthetic aperture radar or hyperspectral Earth 

imaging, that produce volumes of data far beyond 

the capacity of radio-frequency downlink systems. It 

is also possible to use these satellites as data relay 

nodes in low-Earth orbit; a modest constellation 

of small satellites has the potential to provide lowlatency, high-rate communications as a service for 

other satellites in orbit around Earth.

The OCSD satellites are developed and operated by 

The Aerospace Corporation of El Segundo, California.

The OCSD mission is managed and funded by the 

Small Spacecraft Technology Program (SSTP) within 

the Space Technology Mission Directorate. The 

SSTP expands U.S. capability to execute unique 

missions through rapid development and in space 

demonstration of capabilities for small spacecraft 

applicable to exploration, science, and the commercial 

space sector. The SSTP will enable new mission 

architectures through the use of small spacecraft with 

goals to expand their reach to new destinations, and 

challenging new environments.

For more information about the SSTP, visit:

www.nasa.gov/directorates/spacetech/small_spacecraft/

For more information about OCSD, please contact:

Richard Welle

Senior Scientist, Space Science 

Applications Laboratory 

The Aerospace Corporation

Richard.P.Welle@aero.org

Roger C. Hunter

Small Spacecraft Technology Program Manager

Space Technology Mission Directorate

NASA Ames Research Center

Roger.C.Hunter@nasa.gov

Christopher E. Baker 

Small Spacecraft Technology Program Executive 

Space Technology Mission Directorate 

NASA Headquarters 

Christopher.E.Baker@nasa.gov The OCSD 1.5U CubeSat Transmits Data Via Laser 

from Space to Ground.

National Aeronautics and Space Administration

Ames Research Center

Moffett Field, CA 94035

FS-2018-07-02-ARC NASA Facts