Gator-SATComms & Mission Control

UF Small Satellite Specification Document

Subsystem: Comms & Mission Control

Sean Szopinski,

Andres Gonzalez-Ariza,

Frank Monzon,

Initial Release Date:12.1.06

Signature Page

Reviewed by:
Name, Title, email / Date
Reviewed by:
Name, Title, email / Date
Reviewed by:
Name, Title, email / Date
Reviewed by:
Name, Title, email / Date

Revision History

Revision / Description / Author / Date / Approval
1 / 1stDraft / Sean, Andres, Frank / 09/07/06 / Pending
2 / 2nd Draft / Sean and Andres / 12/15/06 / Pending
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Table of Contents

1…………………………………………………………SCOPE

1.1……………………………………………………….GENERAL

2………………….……………………………………….APPLICABLE DOCUMENTS

2.1 ………………………………………………………...GOVERNMENT DOCUMENTS

2.2…………………………………………………………INDUSTRY DOCUMENTS

2.3…………………………………………………………GATOR-SAT CCDH DOCUMENTS

3…………………..……………………………………….REQUIREMENTS

3.1…………………………………………………………ITEM DEFINITIONS

3.1.1……………………………………………………….FUNCTIONAL BLOCK DIAGRAM

3.1.2.…………………………………………………….....INTERFACE DEFINITION

3.1.2.1……………………………………………………...PHYSICAL

3.1.2.2…………………………………………………...... ELECTRICAL

3.1.2.3……………………………………………………...FUNCTIONAL

3.2……………………………………………………….....CHARACTERISTICS

3.2.1……………………………………………………...... INDUCED ENVIRONMENTS

3.2.2………………………………………………………..CLEANLINESS

3.3…………………………………………………………..PROTOTYPE

4…………………………………………………………….APPENDICES

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Gator-SATComms & Mission Control

Specification for Command, Communications, and Data Handling

  1. Scope
  2. General: This specification establishes the design, construction, performance, development, and test requirements for the Command, Communications, and Data Handling subsystem of the Gator-SAT (GSAT), herein referred to as the CCDH.

The CCDH is the operational heart of the GSAT. It is responsible for controlling all of the GSAT’s functions and communications during the mission period. All communications equipments, data storage activities, and commands processing fall under the CCDH jurisdiction.

The primary challenge of the CCDH group is designing a system that can handle all of these responsibilities while under the severe limitations of the GSAT. The CCDH must be small enough to fit within the 10 cm3volume of the GSAT along with all of its other subsystems. Additionally, the CCDH must operate with less than two watts of power.

According to the mission of the GSAT, the CCDH must also provide visual confirmation of the deployment of the deorbiting system. To accomplish this, the CCDH must include a camera and the capability to transmit picture data.

  1. Applicable Documents

The following documents of the exact issue shown shall form part of this specificaion to the extent specified herein. In the event of conflict between the requirements of this specification and any referenced document the order of precedence shall be 1. The contract, 2. This specification, 3. Referenced documents.

2.1Government Documents:
Appendix A.1 Federal Communications Commission (FCC) frequency and call-sign allocation request instructions
Appendix A.2Amateur Radio Operator Exam Description, FCC Website
Appendix A.3 Quick form application for authorization in the ship, aircraft, amateur, restricted and commercial operator, and general mobile Radi Services (FCC 605 Main Form)

2.2Industry Documents:
Appendix B.1 Communications Terminologyby Satcoms UK
Appendix B.2 Satellite Communications Tutorial by J P Silver
Appendix B.3 Overview of the CubeSat Kit by Pumpkin,Inc
Appendix B.4 Calpoly FCC Frequency and callsign allocation request
Appendix B.5 PicoPacket capabilities overview, PacComm Website
Appendix B.6 Detailed Design Review for Communications & Data PowerPoint presentation by Adam DarlingArmando llauro, and Matt Kruse

2.3Gator-SAT CCDH Documents
Appendix C.1 Link budget
Appendix C.2 FCC Frequency and callsign allocation request

  1. Requirements
  2. Item definitions:

The Pumpkin CubeSat

Figure 3.1: Skeletonized CubeSat Kit

The Pumpkin CubeSat Kit is the defining structure of the GSAT. It is a 10cm cube designed to be loaded into a P-POD launching system. The surface must be free of protrusions in order to fit safely into the launcher, and the corner contact rails must be unaltered. The total mass of the GSAT must also be less than one kilogram. The interior of the CubeSat holds the included flight module board and up to four PC/104 boards.

The FM430 Flight Module

Included in the CubeSat Kit is the FM430 Flight Module (Figure 3.2). The FM430 is based around and named for the Texas Instrument’s MSP430 microcontroller(see Appendix B.3). The MSP430 is a very common chip used in picosatellites. It has all the functionality required for the G-SAT mission, operates on less than two milliamps, and meets the structural and thermal requirements for low earth orbit.

Figure 3.2: FM430 Flight Module

The FM430 includes a USB-2.0 port to connect the CubeSat to a PC to conduct software diagnostics. This port can also power the CubeSat up to 500mA maximum current. All of the bus connectors are rated over 2A continuous current, safely above the maximum expected current on the CubeSat.The flight module runs on mixed +5V/+3.3V operation. Components can draw either voltage level from the bus. A mission specific Electrical Power System (EPS) must be designed to direct power to the kit components.The flight module consumes 2-20mW during operation. On standby mode, the power consumption is reduced to 10µW.

All the data and specifications on the CubeSat Kit can be found in Appendix B.3

The Transceiver

The radio transceiver is being designed and built by Ivan Galysh of the Stensat Group ().The transmit (TX) frequency of the radio for downlink is in the 70cm ultra-high frequency (UHF) band. The receive (RX) frequency of the radio for uplink is in the two meter very-high frequency (VHF) band. The current design iteration runs on 0.770mA at five volts for an output power of two watts. This is higher than the expected available power, and the radio will be capable of running at reduced power input. The radio supports frequency-shift key modulation (FSK) at 1200 baud. The dimensions of the radio are not yet available.

The PicoPacket TNC

Figure 3.3: Basic TNC in housing Figure 3.4: Stripped TNC board and GPS board

The terminal node controller (TNC) connects the GSAT’s processing and data storage hardware to the radio. The TNC is responsible for converting the analog (radio) signal to digital data that can be interpreted by the processor, and vice-versa.The PicoPacket TNC (Figure 3.3) is the most common choice in picosatellite design. It is capable of 1200 baud data transfer and operates at 50mA. The standard model is 25 x 63 x 83 mm in size, and is GPS capable. The TNC housing will be removed as in Figure 3.4 to decrease the required volume.

Antenna

The GSAT will require two antennas, one for uplink and one for downlink. Quarter-wavelength antennas will be utilized to conserve space, 50cm for uplink and 18cm for downlink. They will be constructed of metallic tape and oriented on the side of the GSAT so that their radiation pattern is ideal. The exact configuration will need to be tested extensively to produce the best results.

Ground Station

The Gator Nation Earth Station (GNES) will function as the GSAT’s primary ground station. GNES is well equipped to compensate for the low radio signature of the GSAT. The station is run by the Gator Amateur Radio Club (GARC), and all CCDH staff must be members of GARC. Additionally, an FCC Technician’s License is required to operate the equipment at GNES. The station is equipped with a DB-218 UHF/VHF antenna array (Figure 3.5), a Yaesu G-5500 rotator, and an Icom IC-910H radio.

Camera

To determine the state of deployment of the payload and return visual confirmation a complementary metal–oxide–semiconductor (CMOS) camera will be installed with the payload of GSAT.A low resolution, colorless image will provide confirmation without the need for a large file size. The CCDH system will transmit this image back to the ground station for analysis.

Figure 3.5: GNES antenna array

3.1.1Functional Block Diagram:

Figure 3.6: CCDH Structure

3.1.2Interface Definition: The TNC connects directly to the flight module. The radio transceiver is connected to the TNC, and the antennas are connected to the radio. The TNC and radio are powered through the connection to the flight module, which is directly connected to the power supply. The ground station communicates to the GSAT through the uplink and downlink of the radio signal.

3.1.2.1.Physical: The flight module is seated directly against one of the cube faces to line up with the various connection slots machined into the CubeSat skeleton. The TNC is seated directly on top of the flight module board. The radio position is flexible and will be placed to best suit the needs of the attitude control group. The antennas will be mounted on the same face with opposite orientations to prevent cross contamination of the TX and RX signals.

3.1.2.2.Electrical:

Figure 3.7: Flight Module Connection Diagram

3.1.2.3.Functional: The command information is transmitted to the satellite by FSK modulated analog signal and is received by the antenna and passed to the radio. The signal is decoded by the radio, which sends the information to the TNC. The TNC converts it to digital to be processed and executed by the MSP430 microcontroller. The process is reversed for data downlink.

3.2.Characteristics:The performance of the CCDH system and GNES ground station are outlined in the Link Budget (Appendix C.1).

3.2.1Induced Environments: The CCDH subsystem shall continue to function as described by this specification through the launch process and its mission period in low earth orbit. All of the subsystem’s components have been used in previous picosatellites and are field proven. Additionally, all components meet the expected temperature and radiation requirements.

3.2.2Cleanliness:During assembly of the GSAT all precautions will be taken to eliminate foreign or loose materials from entering the GSAT. Gloves will be worn to prevent the spread of body oil, while component pieces will be tracked and counted to prevent misplaced fasteners from being left inside the assembly.

3.3Prototype: The first CCDH prototype will be constructed using the PicoPacket TNC, a packet radio capable of UHF/VHF operation, and a laptop. Operational conditions will be simulated by the prototype in order to test the link between it and GNES.

Appendix A

Government Documents

Appendix B

Industry Documents

Appendix C

Gator-SAT CCDH Documents

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