AMSAT OSCAR-E, ADCARS, and "Eagle"

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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, 1300-1700 EDT NASA Goddard Space
Flight Center Greenbelt, Maryland
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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.

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AMSAT OSCAR-E (AO-E)

• 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.

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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 AMSATs 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
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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

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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
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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 satellites surface area is
  covered by solar cells.
• The remaining surface area is covered with
  thermal absorbing and reflective tape.
• A separation mechanism.

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AO-E Attitude Control

• Two magnetic rods that align the satellites
  vertical axis with the Earths 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.

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AO-E Central Processor Hardware

• 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.

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AO-E Spacecraft Flight Software

• 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

A new antenna design on the roof at SpaceQuest,
20-Apr-2002
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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.

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AO-E Command and Control

• Bootloader communicates with AO-Es 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!
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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
  lt1 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
• lt40 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.

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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 gt60 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.

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AO-E Space for Optional Payloads

• 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

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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.

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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

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Robust Telemetry LinkA Design Example
Demonstrate the value of using FEC and
interleaving to improve telemetry reception by
ground stations.

• 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?).

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Project Eagle(Was Project JJ)
Demonstrate the value of using FEC and
interleaving to improve telemetry reception by
ground stations.

• 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