External ISS Experiment in the Amateur Satellite Service
US Naval Academy Satellite Lab
Bob Bruninga, WB4APR

Midn 1/C Otero, Silver, Jones, Kolwicz, Evans, and Henry

PCSAT2 STATUS: PCSAT2 is COMPLETE and ready for launch. Last Functional Test OK on 13 Jan 2005

  • Launch on Space Shuttle is slated for the first return-to-space mission.(12 May 2005)
  • Delivery to Cape planned for 18 Jan 2004
  • A new web page has been formed for PCSAT2 Operations
  • Thermal-Vac completed on 17 Dec 2003. Download .XLS spread sheets. The only apparent temperature dependencies were about 180 mA delta in Iload and Ibat and about 5 mA on RXB as shown on the last two current plots.
  • Flight integration at NRL began in Sept 2003

    PCSAT2/MISSE5/PEC: MISSE is a Materials International Space Station Experiment using a Passive Experiment Container (PEC) to fly space environment samples to space and back. It has flown 4 times including a year on MIR as MEEP. It is attached to the exterior of the ISS during an EVA to expose its samples to space. For MISSE5, these samples are high-tech DOD solar cells on the side of MISSE that faces the sun. On the back side, the Naval Academy has an opportunity to add an Amateur Satellite Communications system similar to what it is flying on PCsat as an external ARISS payload.

    The PCSAT2comm system will operate in the ITU Amateur Satellite Service in cooperation with ARISS and provide a PSK-31 multi-user transponder, an FM voice repeater for possible use with ISS Crew communications and an AX.25 packet system for use as a UI digipeater and for telemetry, command, control. The PEC is basically a suitcase for travel that opens in space as shown above. The solar panel side of the PEC will contain new technology solar cells and the housekeeping telemetry from PCSAT2 will include data on the techincal investigation of the radiation effects on these cells. See the Paper on PCSAT2's operation in the Amateur Satellite Service or the Full ITU rules as published by the IARU .

    See PEC drawing deployed

    SPONSORING ORGANIZATION: The Telemetry/Command/Communications project called PCSAT2 will be conducted under the USNA Small Satellite program with the guidance of LTCL Billy Smith and Satellite Lab Senior Research Engineer, Bob Bruninga, WB4APR. The USNA Amateur Radio Club would be the spacecraft operating organization. Since PCSAT2 will fly on the ISS, its operations will be fully coordinated with the ARISS (Amateur Radio on the ISS) international team.

    PCSAT2 DESCRIPTION: PCSAT2 will use the same dual redundant AX.25 command and control system as used on PCsat (NO-44) offering 8 on/off commands, 5 telemetry channels and a serial port for the solar cell experiment telemetry. It also supports the Digital Comms Relay support of the PCsat/APRS mission. The packet uplink is on 145.825 MHz and the default downlinks are in the 435 MHz band to avoid any possible interference with existing ARISS missions. PCSAT2 will have quad redundant transmit inhibits for EVA safety issues, thus, it is also easy to turn off to avoid any issues with other UHF ARISS experiments that may be activated in the future. Also, the mission lifetime of PCSAT2 is only 1 year, because it is a sample-return mission, thus terminating any long term conflicts in spectrum management.

    BAND PLANNING: One of the key issues with any Amateur Radio experiments on ISS is the requirement to avoid any mutual interferece between systems. For this reason, ARISS will need to eventually move all uplinks and downlinks into separate bands. This is so that multiple uplinks and multiple downlinks can be going on simultaneously. As it is, with both uplinks and downlinks on 2m, that band cannot be shared without mutual interference. Thus PCSAT2 is having to be designed as mode J to avoid transmitting on 2m, even though mode B (downlinks on 2m) is far superior to reaching schools and low-tech stations and meeting our mission objectives. There is much UHF equipment being planned for ISS, but until it is operational and ARISS has a long range plan, we are stuck with mode J. Ultimately, we think all ISS downlinks should be on 2 meters and are working up a draft paper to that regard. In the mean time, here is a possible band plan idea.


    The PCSAT2 mission is intended as an opportunity to augment existing ARISS communications experiments with an external autonomous communications payload. In this regard, it has three potential uses:

  • A UI-Digipeater to help ease congestion on the currently shared ARISS PMS (Packet Mail system)
  • A PSK-31 transponder for multi-user communications to improve accessibility for schools and ARISS outreach programs.
  • An FM Voice repeater for full duplex crew communications to facilitate crew-to-school ARISS contacts.

    USER RECOMMENDATIONS: As was the case for PCsat, and in accordance with the rules for operation in the Amateur Satellite Service, all duly licensed operators worldwide are welcome to use the PCSAT2 transponders in accordance with the published guidelines. To keep users fully informed of their expected uplink requirements, we will publish and maintain an active and current User Service Agreement for guidance to all users.

    This kind of open publishing of the detailed user expectations pioneered by PCsat was entirely successful and we were very pleased that Amateur Satellite Operators worldwide in general adherred well to the recommendations for the benefit of all.


  • Antenna details:... Plan, Corner Plate, the Drawing and New idea, EZNEC antenna model.
  • Antenna Photos:.... Corner Hinge Assy, Corner PCB and tuning ckts, Closeup details.
  • Antenna Phasing:. UHF , VHF , Matching Ckt, PCB Layout, T/R sw, Assembly Notes.
  • Assembly Plans:... Interface Brd, Phasing Board, Receivers, TXA, TXB, and TXC. Ibrd/TNCs.
  • Command Ckts:.. List, Schematic, TXA/C ckts, TXB/RX/Heater ckts, TNC Resets, and XCD Hold Off.
  • Communications:. Block Diagram . PSK31 10m RX photo1, Photo2, and Photo3.
  • DTMF System:.... DTMF details, SPEC, ARISS CMD Screen, DTMF mounting details.
  • EVA Safety:....... TX Inhibit Plan , Block diagram , and Detail Schematic .
  • Failsafe timers:.... 96 hour timers.
  • Firmware Items:.. TNC Firmware defaults.
  • Fuse Selection:.... Use of PTC fuses in Vacuum rated at 50%. 100 ma Fuse 1.1 amp Fuse
  • Frequencies:........ PCSAT2 Operations in the ITU Amateur Satellite Service and the IARU Rules.
  • Ground Equipt:... GSE connector, User Equipment, EMI Test config, and GSE Test Setup.
  • Interface Board:.. Elements, Layout, Audio Ckt. Assy plan, Test Plan,and D1K mods.
  • Mechanical Items: Shelf Detail, PEC box, Handrail clamp, and a Connector Location sketch.
  • Material Items:.... Parts List.
  • Operations Plan:... Telemetry Collection Plan, Operational Modes,
  • PSK-31 Items:.... Miroslav Kasal's 29 MHz PSK-31 Receiever schematic .
  • Power System:.... Distribution Ckt, Comms Power Budget, and the Actual Power Budget.
  • Prototype Photos:..... Prototype TX and TNC pan.
  • Radiation Test:.... DTMF Radiation test .
  • Requirements:...... Initial concept requirements for the AX.25 system.
  • RF Subsystem:.... RF Functional Block Diagram and Frequency compatibility with ARISS.
  • Telemetry Items:... Channel Plan, Multiplexer, Telemetry Eqns, and the First TLM data.
  • Test Plans:............ Interface Board , SolarEx<=>IBoard , RF System , System Level , 96hr timer.
  • TNC Modifications:... KPC-9612 Mods
  • Thermal Items:..... An early Thermal Approximation
  • Unresolved ideas:..Possible LED Status Indicators (not implemented).
  • Wiring Items:......... Cables , Harness , Original Coax , Final Coax , RX internal and TX internal .

    Click for high-res

    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, 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:

  • Terminal Node Controller (photo)
  • TNC mods for telemetry
  • UHF 2 Watt Transmitter (photo) (VHF shown, but UHF is similar)
  • VHF receiver (photo)
  • Evolution/Chronology of this project.

    The AX.25 segment of the PCSAT2 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 PCSAT2 Communications mission is a project to produce a viable external ISS payload in a very short time frame using off the shelf components where possible. Here are the background topics of design:


  • PHOTO of original RF model with MLI blanket.
  • Alternate Antenna idea.
  • Connector assignments,
  • Board layout
  • 8 hour timer inhibit 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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    Midshipmen Amateur Radio Club