AMSAT OSCAR-E, ADCARS, and "Eagle"

1. AMSAT OSCAR-E, ADCARS, and "Eagle" Presented by Richard M. Hambly (W2GPS) AMSAT-DC MEETING AND SPACE SEMINAR Maryland-DC area AMSAT Meeting and Space Seminar Sunday, May 5, 2002, 13:00-17:00 EDT NASA Goddard Space Flight Center Greenbelt, Maryland

2. AMSAT OSCAR-E, "Eagle", and ADCARS • AMSAT OSCAR‑E is a new LEO satellite from AMSAT-NA. • ADACRS is “Advanced Data Communications for the Amateur Radio Service • “Eagle” is a new HEO satellite from AMSAT-NA.

3. AMSAT-NA is back in the satellite business! 12 years since AMSAT-NA built and launched the original Microsats, AO-16, DO-17, WO-18, and LO-19 in 1990. 8 years since AMRAD-sponsored AO-27 was launched in 1993. AMSAT OSCAR‑E is a new Low Earth Orbit (LEO) satellite AMSAT is returning to the practice of designating LEO satellites by sequential characters. This was last done for AMSAT OSCAR‑D, which became AMSAT OSCAR‑8 after launch and commissioning. AMSAT didn't use letters for the first four Microsats Phase 3 series started again with “A”. Space and power are available for one or more optional payloads that will be provided by AMSAT volunteers. AMSAT OSCAR-E (AO-E)

4. AO-E Introduction • A Microsat class spacecraft weighing approximately 10 kg. • Consists of five solid aluminum trays, each with four walls and a bottom stacked to form approximately a 10-inch cube structure. • Six solar panels attach to each of the six sides. • Several antennas protrude from the top and bottom surfaces. • Similar to AMSAT’s original Microsats (AO-16, DO-17, WO-18, and LO-19). They were followed by the descendents of that legacy, including IO-26, AO-27, MO-30, and SO-41. Dick Daniels W4PUJ at SpaceQuest 28_Feb-2002

5. AO-E Block Diagram • Four VHF receivers • One Multi-Band Multi-Mode Receiver • Two UHF transmitters • Six modems • Flight computer • RAM disk • Batteries • Battery charger and voltage regulators • Wiring harness • RF cabling • RF switching and phasing networks • 56 channels of telemetry • Magnetic attitude control

6. AO‑E Core Subsystems • Physical structure • Attitude control • Central processor hardware • Spacecraft flight software • Power generation and distribution • Command and control • A basic set of receivers, transmitters and antennas • Space for optional payloads AMSAT Board visits SpaceQuest, 20-Apr-2002

7. AO-E Physical structure • A stack of five machined aluminum modules, each 9.5” x 9.5”. • The height of each module is adjustable up to a total of 9.5 inches. • Nominal useful internal area is approximately 8 inches x 7.5 inches. • RF cables and a wiring harness carry power, inter-module data, telemetry, and control signals. • Four machined rods running the height of the spacecraft bolt the assembly together. • Passive thermal control system • Almost all of the satellite’s surface area is covered by solar cells. • The remaining surface area is covered with thermal absorbing and reflective tape. • A separation mechanism.

8. AO-E Attitude Control • Two magnetic rods that align the satellite’s vertical axis with the Earth’s magnetic field. • Allows one end of the satellite to point generally towards the earth. • Four hysteresis damping rods that control the satellite spin rate. • Reflective/absorptive tape that cause the satellite to rotate about its Z-axis as a result of solar photon pressure. • Solar-induced spin averages out the thermal load on the satellite. • Limitations • The satellite makes two rotations per orbit resulting in one face favoring the Northern Hemisphere and the opposite face favoring the Southern Hemisphere. • The Earth-pointing direction is on the order of ±20 degrees in the temperate zones, varying with orbital inclination.

9. Flight-proven, low-power NEC V53A processor clocked at 29.412 MHz. EPROM has redundant sections. Main memory system is error-detecting and correcting (EDAC) using bit-wise triple mode redundancy (TMR). 16Mb RAMDisk for bulk data storage. 16Mb Flash memory for rapid re-booting of the OS and applications. Six (6) GMSK modems - 600 bit/s to 115.2 kbit/s. Eight (8) open collector N-channel FETs provide power switching. Serial Peripheral Interface (SPI) bus links telemetry boards to CPU. Memory Boot EPROM Six Six - - Channel Channel V53A @ 29.4 MHz V53A @ 29.4 MHz Boot EPROM 1 MByte TMR EDAC 1 MByte TMR EDAC FSK Modem FSK Modem DMA Interrupts DMA Interrupts Dual 128K Byte RAMDISK RAMDISK CMOS Digital I/O CMOS Digital I/O FPGA Logic FPGA Logic 16M Byte 16M Byte Open Open - - Drain Drain NFETs NFETs FLASH FLASH SPI Ports SPI Ports 4MByte – 32MByte 16MByte AO-E Central Processor Hardware

10. Boot loader verifies satellite health and loads the operating system Sends acknowledge beacons Uploads new software Downloads memory locations Peak and Poke memory and I/O Loads software from FLASH or error-detecting and correcting memory (EDAC) Executes OS by command or timer Operating System Moved from EPROM to RAM by the boot loader Detailed telemetry reporting Power system control Control of transmitters and receivers Minimal attitude control OS Support Tasks Memory file manager File Transfer Tx Scheduling and Power Monitoring Supervisor Task Loader and Monitoring Mission Software provides complete control over all aspects of the satellite Advanced Task Supervisor TX and RX multiplexing and control Telemetry monitoring, storage and reporting RAMDISK management Communications protocol Scheduling for regional satellite access Magnet torquer and IR attitude control Optional experiment control AO-E Spacecraft Flight Software A new antenna design on the roof at SpaceQuest, 20-Apr-2002

11. AO-E Power Generation and Distribution • Battery Control Regulator (BCR) converts solar panel power to system power, and manages battery charge and protection. • Switching design with 89% efficiency. • Operates autonomously. • CPU can fine-tune default parameters. • Multiple switched 8-V lines for high power applications such as Transmitters. • 3.3-V and 4.6-V switching regulators, each with 250 mA output, with multiple switched and unswitched outputs. • Separation-switch circuitry. • External connection port with two levels of separation switch override. • GaAs Solar Panels on all sides of AO‑E produce about 16 volts at a minimum efficiency of 19%. • Battery is six NiCd 4.4 Ah cells with a nominal battery voltage of 8 V DC.

12. AO-E Command and Control • Bootloader communicates with AO‑E’s bootloader to upload code changes, or to load and execute the OS and tasks. • Housekeeping communicates with each of the tasks onboard the satellite. Its primary use is to configure the satellite. • Telemetry Gathering and Reporting downloads and displays satellite health information. Mark Kanawati N4TPY with “FlatSat” 20-Apr-2002 Note: each of these programs need to be written or re-written by AMSAT volunteers!

13. AO-E Receivers and Antennas • VHF antenna is a very thin ¼ wave whip in the center of the top surface of the spacecraft. • Feeds the low insertion loss bandpass filter, then • a GsAsFET Low Noise Amplifier with a noise figure <1 dB and 18 dB gain, then • a second bandpass filter, and • a four-way power divider that channels the incoming signal into four VHF receivers. • Four miniature VHF FM receivers • <40 mW each and weigh less than 50 gm. • Typical sensitivity is –122 dBm. • IF bandwidth 15 kHz or 30 kHz, based on data rate requirements.

14. AO-E Transmitters and Antennas • Two UHF FM transmitters that each have a PLL-based exciter and a Motorola high-power amplifier. • Small size and low mass. • High efficiency. • On orbit adjustable output power from 1 to 12 watts. • Nominal operation is at 7.5 volts. • Analog or digital data rates up to 56 kbit/s and beyond are possible. • The overall gain of the UHF power amplifier is 39 dB. • Up to 12 watts of RF output at >60% efficiency excluding the 2mW exciter. • Both transmitters can be operated at the same time into a single antenna system. • UHF Turnstile Antenna is fed by hybrid antenna phasing network to each of four output antenna ports with less than 0.5 dB of insertion loss.

15. Advanced Data Communications for the Amateur Radio Service (ADCARS) L-Band/S-Band Communications System GPS Receiver Active Magnetic Attitude Control Audio Recorder Experiment Low Frequency Receiver APRS PSK-31 Multi-band Receiver/Antenna High Efficiency Solar Arrays Robust Telemetry Link AO-E Space for Optional Payloads

16. AMSAT OSCAR-E (AO-E) Summary • Analog operation including FM voice. • Digital operation including high speed APRS. • Higher downlink power. • Multiple channels using two transmitters. • Can be configured for simultaneous voice and data. • Has a multi-band, multi-mode receiver. • Can be configured with geographically based personalities. • Has a true circular UHF antenna that maintains its circularity over a wide range of squint angles. • Higher data rates on downlinks. • Autonomous, self-healing, high efficiency power management system. • Store and forward with continuous monitoring and geographically defined data forwarding.

17. Advanced Data Communications for the Amateur Radio Service (ADCARS) Apply digital encoding techniques to improve communication links and bandwidth utilization. • Wide-band TDMA single frequency data link for multiple simultaneous users and modes. • voice, data, video, telemetry, etc. • S-band downlink, due to bandwidth requirements. • L-band uplink. • Optional signal regeneration. • Optional integration with on-board systems. • File transfer • Telemetry Channel capacity: where: C = channel capacity, bits/sec B = channel bandwidth, Hz S = signal power, W N = noise power, W • Data communication • MPEG recordings

18. Encoding and Interleaving Reed-Soloman + Interleaver + Convolutional Encoder, as proposed by KA9Q for AO-40. Supports worst case operations. Provides link gain. Possible link designs 9600 baud FSK, as implemented in the Kenwood TM-D700A and TH-D7AG so that APRS UI frames can be interspersed with the telemetry. 56K bps GMSK for max throughput. There is no possibility of 1200 bps AFSK on this satellite. AO-E Architecture Constraints All data goes to an NEC 72001 SCC. Then to an FPGA shaping circuit. Then to the varactor modulator. Data rates from 600 to 64K baud. Design Flexibility Full control over the SCC. Some control over shaping in FPGA. Can adjust the amplitude and offset of signal to varactor. Implementation Software in IHU. Hardware + Firmware (PIC?). Robust Telemetry LinkA Design Example Demonstrate the value of using FEC and interleaving to improve telemetry reception by ground stations.

19. Launch Vehicle Has a big impact on physical design. Orbit GTO is lowest cost vs. performance. Propulsion Probably needed to raise perigee. May be needed for reentry. Size and Weight Approx 50 kg, 50-60 cm. Spin Axis Jansson – point at user at apogee. Johnson –perpendicular to plane of orbit. Solar Panels and Power Antennas Project Eagle(Was Project JJ) Demonstrate the value of using FEC and interleaving to improve telemetry reception by ground stations.