AeroCube-7 Ready for Duty as Atlas V Prepares for Launch
Riding on the coattails of its older siblings, AeroCubes 1 through 6, the first in the AeroCube-7 (AC-7) trilogy sits aboard an Atlas V at Vandenberg Air Force Base, California, awaiting its day in the sun. Launch is currently scheduled for Oct. 8, with the remaining two CubeSats in this series set for launch in spring 2016.
The AeroCube-7 trilogy, supported by the Space Technology Mission Directorate (STMD) at NASA headquarters in Washington, D.C., is designed to demonstrate two different capabilities — high-speed optical transmission of data, and small spacecraft proximity operations. NASA calls the overall mission the Optical Communications and Sensor Demonstration (OCSD) mission.
The first AC-7 flight is a pathfinder that will demonstrate most of the subsystems required for both OCSD missions and will be used to evaluate the performance of the attitude-control system. The pathfinder is also expected to demonstrate optical downlinking at speeds up to 100 megabits per second to a ground-based 30-cm telescope using an advanced attitude-control system and a moderate-power, tightly-focused laser beam.
“Much of the pathfinder’s mission is to see how fast we can communicate to Earth from a CubeSat in low-Earth orbit,” said Dr. Richard Welle, Microsatellite Systems Department, Space Materials Laboratory, Technology and Laboratory Operations (TLO), Engineering and Technology Group (ETG).
The second phase of the mission will address the need for low-cost sensors that small spacecraft can use to help them maneuver and operate safely while in close proximity to other spacecraft or objects in space. This 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.
According to NASA, the Block II AC-7 satellites will be modified and upgraded as necessary to incorporate any lessons learned from the pathfinder mission and the laser communication system will be tuned to higher data rates provided they can be supported by the attitude-control system. Additionally, the Block-II satellites, flying together, will perform the proximity operations demonstration.
The mission is funded through NASA’s Small Spacecraft Technology Program (SSTP) within STMD. SSTP was created, according to NASA, specifically to develop and demonstrate new technologies and capabilities for small spacecraft.
These tiny spacecraft, commonly referred to as CubeSats, are power challenged due to their small size. They can collect and store a relatively small amount of energy, an essential ingredient for performing many operations in space. This power challenge makes it difficult to meet the large power requirements typical of high-bandwidth data transmission systems.
Laser communication offers the potential for high-bandwidth communications at power levels well below comparable radio-frequency systems.
“These AeroCubes represent a continuing commitment to determining what can and cannot be done in such a small package,” said Welle.
A CubeSat is a 10-centimeter (about 4 inches) on a side cube-shaped satellite that conforms to the CubeSat Standard developed by the California Polytechnic State University at San Luis Obispo. These small satellites are most often ejected into space from a Poly-Picosatellite Orbital Deployer (P-POD). The P-POD is the most widely used interface between CubeSats and launch vehicles, and its design is responsible for the iconic cubic shape.
The common thread or tether, pardon the space pun, is that of technology testing and development. “These small satellites give us and others in the satellite business the opportunity to test power, attitude control, and communications features,” explained Welle.
The small size and comparative simplicity of CubeSats encourages rapid development and testing, with a development cycle measured in months instead of the years typical of larger satellites. The entire satellite mechanical design can be incorporated in a single SOLIDWORKS model, which simplifies the design process while making it easier for the design team to identify any potential issues.
Geoffrey Maul, CAD design specialist in the Microsatellite Systems Department, has been the principal designer of several AeroCubes, and brought this experience to the AC-7 design.
“Flexibility is probably the biggest challenge when designing a CubeSat,” said Maul. “When we start a CubeSat design we have to pick a starting point and sometimes that means making certain assumptions that prove to be wrong. It is my job to make sure the physical design can adapt to whatever changes are required when those assumptions change.”
The challenge of flexibility is also a feature that allows CubeSat technology to evolve as fast as it has, ultimately leading to the very-high capacity communication system that will fly on AC-7, Welle added.
For Aerospace’s latest information on the OCSD mission, see http://ocsd.aerospace.org.