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 OPAL is Stanford University’s second Satellite QUIck Research Testbed (SQUIRT) satellite. As part of the Space Systems Development Laboratory (SSDL) the SQUIRT project exposes graduate level students to all aspects of satellite design, construction, testing, and operations. 

Each SQUIRT satellite is meant to be constructed in one year and for only $50,000. The design for OPAL was started in early April of 1995. However, since this is only SSDL’s second satellite, development time was extended. OPAL was launched on January 26, 2000, on board the maiden flight of the Minotaur launch vehicle from Vandenberg Air Force Base.

OPAL’s (Orbiting Picosatellite Automatic Launcher) primary mission is to demonstrate the feasibility of launching multiple picosatellites from a mothership satellite. The satellite’s secondary payloads are an accelerometer testbed and a magnetometer testbed, which will perform component characterization. 

Spacecraft Bus
OPAL is a hexagonal prism, made of quarter-inch aluminum honeycomb panels.  The  spacecraft uses a modular, three-tray approach. Each tray contains a different subsystem. In addition, all major components are shielded from EM interference inside sheet aluminum boxes. 

    Bus Height (without antennas): 23.5 cm (9.25 in) 
    Boom Length: 10 cm (4 in) 
    Outside Radius: 21.0 cm (8.25 in) 
    Mass: 23.1 Kg (51 lb.) 
    Volume Envelope: 27,300 cm3 (1660 in3) 
    Usable Volume: 21,300 cm3 (1300 in3)
Power Subsystem
OPAL is powered by seven solar panels.  Ten re-chargeable Nickel-Cadmium batteries provide backup power. 
    Solar Cells: GaAs, Ge 
    Batteries: Sanyo KR5000DEL, D-size rated at 1.2 Volts and 5 Amp-hours 
Onboard Computer 
OPAL’s computer consists of a primary CPU board and two peripheral data acquisition boards.  All three boards are produced by Vesta Technologies.  The computer controls all aspects of the satellite’s operation, including picosatellite launch, sensor data collection, ground communications, and engineering telemetry. 
    Primary CPU board: SBC332 based on the Motorola 68332 microcontroller, running at 8.38 MHz with 1 MB of onboard RAM. 
    Peripheral boards:  Two SPI332 boards based on Motorola’s Serial Peripheral Interface bus and protocol.  Each board contains 16 digital I/O channels and eight 12-bit analog-to-digital converters.
Communications Subsystem
For ground communication, OPAL uses packet radio transmissions over amateur radio frequencies. The terminal node controller (TNC) and radio transceiver are off-the-shelf units provided by NavSymm Inc.
    Uplink: 70 cm band (437.100 MHz)
    Downlink: 70 cm band (437.100 MHz)
    Data rate: 9600 baud
Picosatellite Payload
The primary mission of the OPAL picosatellite payload is to provide an end-to-end mission demonstration of mothership and daughtership technologies. A storage, deployment, and communication scheme was designed and implemented on the OPAL satellite. The OPAL mothership stored and deployed six picosatellite daughterships.

Three teams designed and constructed the daughterships. A team from DARPA and The Aerospace Corporaiton developed a picosatellite to test MEMS technology and an intersatellite communication network. An undergraduate team, named Artemis, from Santa Clara University used an iterative design process to continually explore the technical capabilities and mission applications of picosatellites. An amateur radio (HAM) team built a transponder picosatellite named STENSAT. 

The OPAL design team developed a scalable, producible, and dependable picosatellite launch mechanism.  A joint OPAL and picosatellite design team developed the daughtership communication scheme. 

Accelerometer Testbed
The accelerometer testbed will characterize the functionality and operation of several commercial-off-the-shelf (COTS) accelerometers. Accelerometer technologies that will be flown include a MEMS capacitive sensor, piezoelectric sensor, an inductive sensor, and a piezoresistive sensor.

Magnetometer Testbed
The testbed consists of a magnetometer made by Applied Physics Systems, and is sponsored by the Relativity Mission, Gravity Probe B. The testbed will characterize the functionality and operation of the magnetometer and may be used to gather OPAL attitude information.

Attitude Control
OPAL is a free-flyer and performs no attitude control. The spacecraft will include ballast so its major moment of inertia is optimal for picosatellite launch. 

Mission Operations
OPAL will be operated from the SSDL ground station, which is fully equipped to carry out satellite contacts over the amateur radio satellite bands.  After the on-orbit checkout period, the picosatellite payload will be the focus of operations followed by an evaluation of the testbed payloads.  Once all the experiments are completed operations will turn to an extensive analysis of vehicle performance.  This will provide valuable information for future SQUIRT-class satellite development. 

Industry Partners
Industry involvement has been critical to the OPAL project.  The following companies have provided invaluable support and advice: Amp, Analog Devices, Analytical Graphics, Dow Corning, Eagle Picher, Harris Semiconductor, ITT Cannon, Lockheed Martin, Motorola, National Semiconductor, PacComm, Pads Software, Penstock, Raychem, Shur-Lok, Space Electronics, Space Systems/Loral, Stanley Tools, and the TiNi Alloy Company. 

For More Information
SSDL Director

    Prof. Bob Twiggs  btwiggs@leland.stanford.edu 
    (650) 723-8651 
OPAL Project Manager 
    James Cutler  jwc@stanford.edu 
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