The Petite Amateur Navy Satellite (PANSAT) is a small satellite designed and built by officer students, faculty, and staff at the Naval Postgraduate School (NPS). The main objective is to support the Space Systems Engineering and Space Systems Operations Curricula by providing a "hands-on" hardware project where exposure to the many facets of a space system development and life cycle can be experienced. PANSAT further provides educational training while in orbit through a space-based laboratory for officer students at NPS. The spacecraft itself provides store-and-forward (packet radio) digital communications using direct sequence spread spectrum modulation. PANSAT operates in the amateur radio 70 cm band with center frequency at 436.5 MHz, a bit rate of 9842 bits per second and 9 MB of message storage. Amateur radio ground stations will be able to utilize PANSAT via a bulletin-board type user interface.

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PANSAT offers officer students an opportunity to gain practical education in Space Systems Engineering and Operations by way of Master's degree theses, class projects and directed study courses. Students hail from diverse backgrounds, representing all branches of the military services as well as numerous foreign countries, and are actively involved in virtually all aspects of the program. Topics include areas such as mission operations, astrodynamics, mechanical and electronic subsystem design, system integration, and protoflight testing. As of June 1998, approximately fifty PANSAT related theses have been completed. PANSAT is also used to provide case studies in Space Systems courses, instructional labs and directed studies at NPS.

Direct-sequence spread-spectrum modulation is a technique that spreads a conventional narrowband signal by mixing it with a bit stream (see diagram). The result is a dilution of the signal energy with respect to bandwidth. The spread-spectrum signal has the same energy per bit as the narrowband signal, but the power density at any one frequency is significantly lower. The signal can be spread to such a point that it is entirely below the noise level of a conventional receiver, making it difficult to detect or intercept. The receiver of a spread-spectrum signal uses the same bit stream to despread the signal. Through the despreading of the signal, conventional signals are suppressed, making it resistant to interference and difficult to jam.

Potential Applications

Through use by the amateur radio community PANSAT will supply a means to demonstrate spread-spectrum communications. In addition, PANSAT provides many potential applications for low-cost communications. The low probability-of-intercept would be an important feature for the military in downed-pilot-rescues. The pilot could obtain his/her location through a GPS system and uplink the information to the orbiting satellite at low risk. Examples of civilian uses include emergency rescue and communication to remote areas.

PANSAT has a robust structural design with high margins of safety and is adaptable to a number of launch vehicles. The satellite is approximately 19 inches in diameter and has no attitude control or propulsion. Eighteen square and eight triangular aluminum panels make up the outer surface of the satellite. Seventeen of the square panels are equipped with solar panels and four dipole antennas are attached in a tangential turnstile configuration to the trianguular plates. The spacecraft structure is composed of two equipment plates, solar panels, and a cylindrical support. The three main spacecraft subsystems are the electrical power subsystem (EPS), digital control subsystem (DCS), and the communications payload.

Testing

To prepare the spacecraft for flight, a comprehensive functional and environmental test plan was implemented at the system and subsystem level. Environmental testing includes thermal vacuum, random vibration, and electromagnetic interference and compatibility (EMI/EMC) testing. Testing was performed at NPS as well as the NASA Goddard Space Flight Center (GSFC) in Greenbelt, MD.

Ground Station

A modified amateur satellite ground station is needed to communicate with PANSAT. The NPS ground station utilizes off-the-shelf software, is micrcomputer-controlled, and is equipped with a spread- spectrum modem. The NPS ground station is similar to a typical amateur radio user station, except it has spacecraft command capability. The NPS ground station is also utilized as a classroom instructional laboratory.