Leonard David's INSIDE OUTER SPACE

A United Launch Alliance Atlas V rocket carrying a National Reconnaissance Office payload launches skyward on Oct. 8, 2015 from Vandenberg Air Force Base. Also deployed were 13 CubeSats.
Credit: U.S. Air Force/Senior Airman Kyla Gifford

A CubeSat recently released in Earth orbit that was to demonstrate high speed optical transmission of data from Earth orbit has run into trouble.

The Optical Communications and Sensor Demonstration (OCSD) satellite was built and managed by The Aerospace Corporation, funded through NASA’s Small Spacecraft Technology Program within NASA’s Space Technology Mission Directorate (STMD).

The Optical Communications and Sensor Demonstration (OCSD) project uses CubeSats to test new types of technology in Earth orbit.
Credit: NASA/Ames Research Center

OCSD was among thirteen NASA and National Reconnaissance Office (NRO)-sponsored CubeSats that were launched aboard a United Launch Alliance Atlas V rocket on October 8 from Vandenberg Air Force Base in California. The booster hurled into orbit a classified NROL-55 spacecraft.

All CubeSats were flown on the NRO’s Government Rideshare Advanced Concepts Experiment (GRACE), which is an auxiliary payload aboard the NROL-55 mission.

Source of the anomaly

The OCSD carries a compact 6 Watt laser to demonstrate high speed optical transmission of data from Earth orbit to the ground.

“After the CubeSat launched last Thursday, initial contacts and checkout of the satellite went well,” said Richard Welle, Director of the Microsatellite Systems Department at The Aerospace Corporation.

Last weekend, during extensive software upgrades, Welle told Inside Outer Space that the small satellite went through one of its normal reboot sequences in the middle of a software change in the attitude-control system (ACS) processor.

“When the satellite restarted, the ACS processor not only booted into a mode that disabled that processor altogether, it also limited the performance of several other processors. We have reproduced the anomaly in the ground unit, and understand the source of the anomaly,” Welle said.

Beam steering

Is the anomaly solvable?

“At this time, it does not appear that the problem can be fixed in the satellite currently flying,” Welle responded.

According to a NASA/Ames Research Center October 13 statement: “The OCSD satellite is communicating by radio with the ground, but the attitude control system must function properly in order to demonstrate the optical communications system. NASA is discussing the issue with Aerospace as they investigate the problem.”

CubeSats are equipped to evaluate optical laser communications and close proximity maneuvering in Earth orbit.
Credit: The Aerospace Corporation

The OCSD’s mission was to assess the ability to precisely point itself as it demonstrates data transfer by laser. That onboard laser is hard‐mounted to the spacecraft and beam steering is accomplished through precision pointing of the spacecraft as a whole.

Second OCSD mission

The bursts of laser data from the satellite were to be received high atop Mt. Wilson in California, north of Pasadena, at The Aerospace Corporation’s Mt. Wilson Optical Communications and Atmospheric Measurements (MOCAM) station. It houses a 12-inch (30‐centimeter) diameter Cassegrain telescope outfitted with a photodiode detector.

The second OCSD mission — using two satellites — is slated for launch early in 2016. Lessons learned from the earlier flight are to be rolled into the second mission. But along with laser communications testing, the dual CubeSats are also to perform proximity operations.

Each OCSD CubeSat weighs just 5 pounds (2.5 kilograms) and measures about 4 inches x 4 inches x 6.7 inches (10 centimeters x 10 centimeters x 17 centimeters).