AeroCube-3 is an advanced single-unit CubeSat demonstration mission of the Aerospace Corporation, El Segundo, CA, USA with funding provided by the USAF SMC (Space and Missile Systems Center) of the Los Angeles AFB. It is the third AeroCube satellite, following on from AeroCube-1, which was lost in a launch failure on July 26, 2006, and AeroCube-2 which was successfully launched on April 7, 2007, but failed almost immediately after launch - however, not before testing and confirming the utility of a new ground station in El Segundo, CA and taking the first ever picture of another CubeSat in space.
Figure 1: Photo of the CubeSate CP-4 (CalPoly-4) taken by AeroCube-2 (image credit: The Aerospace Corporation)
Compared to its predecessors, AeroCube-3 contains several improvements in its infrastructure, including a redesigned power system, replacing the older system which was responsible for the loss of AeroCube-2. 1)
The mission objectives of AeroCube-3 are:
- Test bus performance
- Photograph LV (Launch Vehicle) final stage
- Further develop mission operations for this satellite class.
Figure 2: Photo of the AeroCube-3 CubeSat (image credit: The Aerospace Corporation)
The AeroCube-3 CubeSat conforms to the CubeSat standard in size (10 cm cube) and in mass (≤ 1 kg). The goal of AeroCube-3 is to demonstrate a two-axis sun sensor and an Earth sensor. These are important pieces of a future guidance, navigation and control system. In addition, the CubeSat includes an inflatable balloon that doubles as a tracking aid.
Launch: AeroCube-3 was launched on May 19, 2009 on a Minotaur-1 vehicle of OSC (Orbital Sciences Corporation) from the commercial MARS (Mid-Atlantic Regional Spaceport) at Wallops Island, VA.
AeroCube was a tertiary payload, with TacSat-3 of AFRL as the primary payload, and PharmaSat-1 (triple cube of 5 kg = nanosatellite) as the secondary. Two other CubeSats, HawkSat-1 of the Hawk Institute for Space Sciences, Pocomoke City, MD, and CP-6 (CalPoly-6) of California Polytechnic State University, San Luis Obispo, were also launched, and together the three satellites were known as the CubeSat Technology Demonstration mission. 2)
Two P-PODs (Poly-Picosatellite Orbital Deployers) were mounted on the fourth stage motor casing. One P-POD contained the triple CubeSat (PharmaSat-1), developed by NASA/ARC. The other P-POD contained AeroCube-3, HawkSat-1 and CP-6.
Figure 3: P-POD (left) with the three cubesats flying on the TacSat-3 mission (image credit: NASA)
After launch, AeroCube-3 was tethered to the P-POD and effectively to the upper stage by means of a 61 m tether. However, the tether broke and AeroCube-3 floated away from the stage.
Orbit: Near-circular LEO, altitude of about 460 km (433 km x 473 km), inclination of about 40.5º.
RF communications: The communications transceiver is of AeroCube-2 heritage, operated in the 900–928 MHz ISM (Industrial Scientific Medicine) frequency band with a data rate of 38.4 kbit/s. - However, the AeroCube-3 receiver's sensitivity at a 38.4 kbit/s data rate is 6 dB better than the previously used AeroCube-2 transceiver. 3)
The AeroCube-3 mission consists of two phases:
• Phase A occurs with the AeroCube-3 tethered to the upper stage of the Minotaur-1 launch vehicle. During this phase, AeroCube-3 will measure its dynamics while on the end of a 60 m long tether attached to a tumbling object (the upper stage). A VGA-resolution camera with a wide-angle field of view will attempt to photograph the upper stage on orbit. A tether reeling mechanism inside the picosatellite can close the distance by drawing in the tether (it operates by ground command).
• Phase B starts when the tether is cut and AeroCube-3 becomes a free-flying CubeSat picosatellite. In this phase, permanent magnets and hysteresis material will align the satellite with Earth’s magnetic field. In this configuration, a sensor suite will sweep Earth’s surface and various experiments can be performed. AeroCube-3 will store the sensor data until it passes over its ground station and the data is downloaded.
• On January 6, 2011, the AeroCube-3 satellite re-entered the Earth's atmosphere. 4)
• The satellite functioned until the end but the project lost the ability to talk up to it after 205 days on orbit. After the loss of that ability, the project just would watch the CubeSat come overhead and sync up with the ground station per design - just to make sure the flight computer and power system were operating nominally. The satellite radio suffered a glitch where it would not acknowledge that the ground station was talking to it and therefore would not accept and execute the commands (Ref. 5).
• The balloon was ejected but did not inflate.
• The AeroCube-3 is operating nominally as of summer 2009. 5)
• The tether to the upper stage broke within hours. Further investigations are planned as to the overall behavior of this demonstration test. In particular, what did brake (?) since the CubeSat rebounded several times (information obtained from the IMU data), indicating that tether strength was probably not an issue.
AeroCube-3 incorporates a semi-spherical (8-panel) balloon of ~ 60 cm diameter when inflated that can serve as a de-orbit device as well as a tracking aid. AeroCube-3 uses an inflation system similar to the one on AeroCube-2. The balloon is meant to deorbit the satellite. The difference in orbit life (with and without a balloon) is estimated to be from 1-3 years (depending on atmosphere assumptions) without a balloon compared with 2-3 months with the balloon inflated. A wide-angle VGA (Video Graphics Array) camera (Comedia C328) pointing in the direction of the balloon will photograph its state of inflation. 6)
3) Christopher Clark, Andrew Chin, Petras Karuza, Daniel Rumsey, David Hinkley, “CubeSat Communications Transceiver for Increased Data Throughput,” Proceedings of the 2009 IEEE Aerospace Conference, Big Sky, MT, USA, March 7-14, 2009
5) Information provided by David Hinkley of The Aerospace Corporation
6) Jerry K. Fuller, David Hinkley, Siegfried W. Janson, “CubeSat Balloon Drag Devices: Meeting the 25-Year De-Orbit Requirement,” The Aerospace Corporation, August 2010, URL: http://mstl.atl.calpoly.edu/~bklofas/Presentations/SummerWorkshop2010/Fuller-balloon_drag_devices.pdf
The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates.