WA8LMF Mirror of WB4APR Website - 21 July 2008 PEC

Telemetry/Command and Communications Payload
US Naval Academy Satellite Lab
Bob Bruninga, WB4APR

Midn 1/C Patterson
Ensign Sillman


  • Sketch of the Antenna System.
  • Preliminary Parts List.

    PEC: is a Passive Experiment Container used to fly space environment samples to space and back. It is attached to the exterior of the ISS during an EVA to expose its samples to space. The Naval Academy has offered to build a telemetry and command/ communications system similar to what it is flying on the PCsat mission as an opportunity to fly a communications payload in the amateur satellite service and to provide Telemetry to the ground on the progress of the exposed samples to the space environment. The PEC is basically a suitcase for travel that opens in space as shown below (and detailed HERE).

    The Telemetry/Command/Communications project would be conducted under the USNA Small Satellite program under the guidance of LTCL Billy Smith and Satellite Lab Senior Engineer, Bob Bruninga, WB4APR. Since it would be flying on the ISS, it would need the concurrence of the ARISS (Amateur Radio on the ISS) international team on the mutual compatiblity of the frequencies used. The proposal is a digipeater uplink on 145.825 MHz and downlink on the 70cm band to avoid any possible interference with existing ARISS missions. It would also include a PSK-31 experiment. Since it has triple redundant transmit inhibits for EVA safety issues, it will also be easy to turn off for an other UHF ARISS experiments that may be launched in the future. Also, the mission lifetime of PECsat is only 1 year.

    The PEC Telemetry/Command/Communications Mission, provides generic UI-Digipeating relay service to help ease the congestion on the current ARISS Packet radio BBS system (Packet Mail system) and a linear PSK-31 to FM transponder for multi-user communications experiments. As an autonomous payload, it also provides basic Telemetry Command and Control for PEC system and any other telemetry:

  • Comm System Battery and Solar voltages, temperatures and currents
  • 3 ON/OFF command switches
  • 9600 baud RS-232 serial data telemetry channel for the PEC samples telemetry.
  • Digital Communications Relay support of the PCsat/APRS mission.


  • Recommended DUAL-Redundant design (see photo)
  • Triple redundant-double fault tolerant TX inhibits design concept.
  • TX power 2 Watts peak transmitting short few second data bursts
  • TX whole orbit duty cycle less than 5%
  • TX/RX/COMM whole orbit average power about 1W
  • Peak solar power needed on single flat array = 20W
  • PEC Environmental Samples TELEMETRY < 20,000 bytes per pass (20% duty cycle/Pass)
  • Amateur Satellite Transponder mission (20% dutycyle over USA)
  • Data would use 9600 baud for Telemetry and 1200 baud for Transponder
  • Eclipse Battery would be 12 volts and under 4 Watt-Hours
  • PEC interface to the Telemetry/Comm system is a single RS-232 port (and some ON/OFF switches)

    The TNC COMM system (one of 2) and the dual receivers and dual transmitters.

    The digital communications relay will operate within the ITU regulations for educational/outreach operations in the Amateur Satellite Service, to provide simple Satellite digital communications for amateur satellite operators and educators and possible remote environmental sensors worldwide Examples . This comms mission will provide a follow-on extension to the educational communications mission of PCsat, Naval Academy Boats at sea, cross country travelers, expeditions, or other travelers far from existing APRS terrestrial communications infrastructure. The Transponder and PEC data is captured by existing PCsat-to-Internet ground stations and fed into the existing worldwide internet linked APRS system. The PEC mission would join ISS, MIR, PCsat and several other on-orbit experiments (ASTARS) that have been conducted over the years leading up to this exciting capability.

    Here are several additional PHOTOS, DRAWINGS and Documents reorganized by topic:

    Mechanical details:

  • TNC mods for telemetry

    Module Details:

  • TNC/XMTR/RCVR diagram and the Dual Redundant version
  • Terminal Node Controller (photo)
  • UHF 2 Watt Transmitter (photo) (VHF shown, but UHF is similar)
  • VHF receiver (photo)

    The Space segment of the PEC communications mission has been demonstrated a number of times in space via PCsat, MIR School tests, the Shuttle SAREX, and the SPRE mission. . It is also a spin off of a previous launch opportunity that we had in 1998 called NATSweb that almost got launched on SEA-LAUNCH.. The PEC Communications mission is a project to produce a viable payload in a very short time frame using off the shelf components where possible. Here are the background topics of design:

    APRS is the Automatic Position Reporting System that the Naval Academy uses for tracking its boats and a variety of other vehicles and networks using the APRS Automatic Position Reporting System . The PEC Communications transponder would be operated under the rules of the Amateur Satellite Service and the rules of the FCC.

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    USNA Satellite Ground Station


    Midshipmen Amateur Radio Club

    WA8LMF Mirror of WB4APR Website - 21 July 2008