MicroEye
General Characteristics:Instruments:
- Function: Multispectral Imaging Satellite
- Dimensions: 3.6 m x 0.5 m x 1.1 m
- Launch Mass: 100 kg
- Electrical Power: 250 W
- Attitude Control: 3-axis momentum biased
- Propulsion: 4x gold gas thrusters
- Telemetry: S Band
Orbital parameters:
- Multispectral Imager (0.35 m telescope 0.75 m resolution, 8 spectral bands)
- Band 1 Coastal Blue (0.40 - 0.45 µm)
- Band 2 Blue (0.45 - 0.51 µm)
- Band 3 Green (0.51 - 0.58 µm)
- Band 4 Yellow (0.58 - 0.62 µm)
- Band 5 Red (0.63 - 0.69 µm)
- Band 6 Red edge (0.71 - 0.74 µm)
- Band 7 Near-IR 1 (0.77 - 0.89 µm)
- Band 8 Near-IR 2 (0.86 - 1.04 µm)
- Orbit height: 500 km
- Orbit inclination: 51.64o
- Design life: 2 years
Overview:
MicroEye is an electro-optical imaging microsatellite manufactured by SDI Space Systems which is designed to be capable of providing on-demand multispectral imagery with a tactically useful resolution which it can then downlink directly to military commanders and intelligence centers in the same pass (<10 minutes within being tasked) without the use of a satellite or ground based relay network.
Instruments:
Multispectral Imager: The primary instrument of the MicroEye is a 35 centimeter optical telescope mounted to the spacecraft with three three aft hard-points which is mated with an SDI deigned 40,000 pixel TDI line scan Silicon CCD camera which is capable of imaging in panchromatic (Pan) mode in the 0.45 - 0.80 µm spectral range or in multispectral (MS) mode with 8 spectral bands. From an altitude of 500 kilometres the satellite's multispectral imager can image a 5.8 x 3.8 km area with a ground resolution of 0.75 - 1.0 meters. Images from the camera are compressed into an NITF format where they can be stored on the spacecraft (up to 600 images) and/or transmitted in real time to a ground station for exploitation.
Spacecraft:
Satellite Bus:The Microeye uses a proprietary SDI designed satellite bus which measures 0.5 m x 0.5 x 1.1 m before solar panel deployment with a launch mass of 100 kilograms including the multispectral imager payload. Electrical power is provided by five deployable solar panels which combined provide up to 250 watts of electrical power to the satellite's electrical power subsystem (EPS). The electrical power subsystem also includes a 16 cell Lithium Ion (Li-Ion) battery made from four 4-Cell commercial laptop batteries which have been wired together.
Attitude Control & Propulsion: The spacecraft's Attitude Determination And Control Subsystem (ADACS) consists of a single star tracker, eight coarse sun sensors placed around the spacecraft body, a 9-axis inertial measurement unit (IMU) including 3-axis MEMS gyros and a 3-axis magnetometer, a GPS receiver, and an attitude control system consisting of three reaction wheels and three magnetic torque rods which can slew the satellite at a rate of up to 3°/s to off-nadir imaging angle of up to 30 degrees° with a pointing accuracy of less than 0.15°. Spacecraft propulsion is via a cold-gas propulsion subsystem which contains two composite-overwrapped pressure vessels storing compressed nitrogen gas, twin pressure regulators, a magnetic latch valve, and four outward-canted gold gas thrusters mounted at the rear corners of the spacecraft which provide 3-axis propulsion and torque control.
Communications: The spacecraft's communications system consists of two S-band (2200.5 MHz – 2394.5 MHz) quadrifilar helix antennas (QHAs) on the nadir end of the spacecraft (one transmit and one receive) and two S-band patch antennas on the zenith end of the spacecraft (also one transmit and one receive) which are used for 2-way communications with ground stations at any satellite attitude. Transmitted data is modulated using offset quadrature phase shift keying (OQPSK) modulation with a maximum data downlink rate of over > 1 Mbps.
Ground Control:
To use the satellite a ground commander first determines the GPS grid coordinates of an area he wished to image (up to 5.8 x 3.8 km) which he then relays using a tactical command post with satellite uplink capability. At each command post requests for imagery from different commanders are and merged and prioritized with imagery requests from other commanders in the same theater where they are then relayed to the nearest MicroEye satlelite as it rises over the theater area. The command software on the satellite processes the received imaging requests and then actuates the satellite using its attitude control system to capture imagery of the target areas with an optimized set of attitude slews, snapping imagery of each target area before rapidly slewing to the next target. Images taken are streamed in real time back to tactical command posts on the ground which then transmits the data back to the requesting commander, the entire process from image request to receiving imagery taking less than 10 minutes.