Space Test Program-H2-Radar Fence Transponder (STP-H2-RAFT) - 07.19.17

Overview | Description | Applications | Operations | Results | Publications | Imagery

ISS Science for Everyone

Science Objectives for Everyone
The RAFT mission is a student experiment from the United Sates Naval Academy that uses picosatellites to test the Space Surveillance Radar Fence and experimental communications transponders.
Science Results for Everyone
A series of radar signals form a virtual sensor web around planet Earth, tracking man-made space debris. This experiment by students from the United States Naval Academy aimed to determine the limits of this radar web in detecting satellites about the size of water bottles, and to test experimental communications transponders. The data will provide the Navy Space Surveillance System (NSSS) with the ability to determine the bounds of these otherwise undetectable small satellites and will enable NSSS to independently calibrate its transmit and receive beams. The International Space Station crew deployed the investigation’s two small satellites and monitored several of their subsystems. Volunteer ground stations tracked the satellites.

The following content was provided by Robert E. Bruninga, and is maintained in a database by the ISS Program Science Office.
Experiment Details


Principal Investigator(s)
Robert E. Bruninga, United States Naval Academy, Annapolis, MD, United States

Information Pending

United States Department of Defense Space Test Program, Johnson Space Center, Houston, TX, United States

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
Department of Defense (DoD) - Retired

Research Benefits
Information Pending

ISS Expedition Duration
September 2006 - April 2007

Expeditions Assigned

Previous Missions
RAFT is a new investigation, it has not been performed in microgravity before.

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Experiment Description

Research Overview

  • Radar Fence Transponder (RAFT) is a student experiment from the United States Naval Academy that will determine the limits of the Space Surveillance Radar Fence in detecting small satellites and test experimental communications transponders.

  • RAFT will use two small cube-shaped picosatellites (5 in on a side), to transmit and receive signals from the radar fence for calibration.

  • RAFT is part of the Space Test Program-H2 (STP-H2) complement that also includes MEPSI and ANDE.

The mission of RAFT is to provide the Navy Space Surveillance System, or NSSS, radar fence with a means to determine the bounds of a constellation of picosatellites otherwise undetectable to the radar fence, and to enable NSSS to independently calibrate their transmit and receive beams using signals from RAFT. This must be accomplished with two picosatellites (RAFT1 and MARScom), one that will actively transmit and receive, and one with a passively augmented radar cross-section. Additionally, RAFT will provide experimental communications transponders for the Amateur Satellite Service, the Navy Military Affiliate Radio System, and the Naval Academy's Yard Patrol Craft.

RAFT was deployed from the Space Shuttle Discovery during STS-116/12A.1 mission on December 20, 2006.

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Space Applications
RAFT will lead to a better system of tracking an increasing population of picosatellites.

Earth Applications
RAFT is a student project at the US Naval Academy Aerospace. This experiment provides students the hands-on opportunity to design and build picosatellites. By using mathematics, engineering and scientific concepts, it will prepare the next generation for careers in the Aerospace industry.

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Operational Requirements and Protocols
The RAFT picosatellites are ejected from the SSPL5510 cargo element, a reusable launcher. The launcher is located in the STP-H2 complement, along with the ANDE and MEPSI experiments, which is in the Space Shuttle cargo bay. The launcher will hold 2 picosatellites, RAFT1 and MARScom, which are 5 x 5 x 5 inch cubes that weigh a combined 7 kg. The crew will use a switch from inside the crew cabin to launch RAFT. Each picosatellite contains 3 antennas that will deploy once launched that will allow RAFT1 to communicate with the NSSS and MARScom to communicate with the Amateur Satellite Service, the Navy Military Affiliate Radio System, and the Naval Academy's Yard Patrol Craft.
The Space Shuttle crew will initiate the launch from inside the crew cabin. The SSPL5510 launcher will release the 2 picosatellites, RAFT1 and MARScom. Once the satellites are in orbit, they will power-on and deploy their 3 antennas.

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Decadal Survey Recommendations

Information Pending

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Results/More Information

RAFT was deployed on December 20, 2006 and de-orbited on May 30, 2007 after 5 months in space. The deployment resulted in an applied torque to the satellites (see image sequence below). Several subsystems on the satellite (solar panel and thermal performance) were monitored. Volunteer ground stations were used to track the satellites. (Evans et al. 2009)

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Results Publications

    Bruninga RE, Smith B, Boden D.  PCsat Success! and follow-on payloads. 16th Annual AIAA/USU Conference on Small Satellites, Logan, Utah; 2002

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Ground Based Results Publications

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ISS Patents

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Related Publications

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Related Websites
RAFT Satellite Project

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image The image above shows the relation of size between nine picosatellites (also known as Cubesats) to a bottle of water. The RAFT experiment will use two picosatellites. Image courtesy of NASA, Johnson Space Center.
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image The sequence of images shows the two RAFT satellite cubes being deployed from the Space Shuttle (STS-116). The bottom photo shows the onset of tumbling of the satellites. Image courtesy of DOD.
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