Earth Observer-Spacecraft Bus (EO-SB)

Integration - Final Preparation for Mass Properties

Artist's rendering of EO-1 in orbit

EO-1 Mount to the Delta II Dual Payload Attach Fitting (DPAF)

Overview
ATK has developed an Earth Observer — Spacecraft Bus (EO-SB) based on the extremely successful EO-1 Spacecraft Bus launched in November 2000.” The EO-SB is directly compatible with most earth-observing operational research mission profiles. The EO-SB baseline launch vehicle is the Delta II 7320-10 in the DPAF configuration. In addition, the EO-SB is compatible with the Taurus and Athena launch vehicles. The EO-SB has been designed primarily for orbits ranging from 400 km through 900 km with adaptive capability to other mission orbits.

Mechanical/Physical Architecture
The EO-SB core system structure is an aluminum longeron-stiffened panel design with top and bottom equipment/payload decks. The EO-SB can minimize the distortion induced into the instrument via a decoupled flexible instrument interface. The closed construction provides an equi-potential faraday cage for the Spacecraft components and is referenced to a single point ground plane. The EO-SB provides easy access to components resulting in a streamlined integration schedule.

Power Subsystem
The EO-SB power subsystem is an unregulated (+28V +/-6Vdc), Direct Energy Transfer (DET) power system that supports one 50-Ah Super Nickel Cadmium battery (baseline) connected directly to the power bus.

Guidance, Navigation, and Control (GN&C)
The EO-SB GN&C subsystem is a 3-axis inertially stabilized system. The generalized control logic allows for the baseline zero-momentum system to have an offset wheel speed bias about a preferred (typically a scan profile) axis to provide additional gyroscopic stiffness to the system. The autonomous onboard safing logic initiates appropriate actions based on input from the distributed parameter sensing elements resulting in graceful mode transitions.

EO-1 Launch from Vandenberg AFB

Reaction Control System Option The EO-SB can accommodate a Reaction Control System, that is based on the EO-1 heritage hydrazine configuration and can be used for precise orbit maintenance functions. RF Communications EO-SB uses S-Band for command and telemetry and X-Band Phased Array Antenna for downlinking science data at 105 Mbps (High Speed Data Chain Option). The S-Band system has two S-Band omni antennas operations for downlink at 2 Mbps, available for science data downlink. The S-Band system is compatible with the STDN, DSN, and TDRSS.

Command and Data Handling (C&DH)
The C&DH and attitude control system (ACS) software resides in the Attitude Control and Data System (ACDS) that contains a 12 MHz Mongoose V processor with 1.8 Gbits of storage. Most subsystems contain a Remote Services Node (RSN), which is a R6000 processor for both 1773 interface and subsystem control. A 1553 data bus is also available. In the High Speed Data Chain option, a separate solid-state recorder is available for more demanding science data storage missions.

Thermal Architecture
The EO-SB has a cold-biased passive thermal architecture using thermostatically-controlled heaters, passive Multi-Layer Insulation (MLI), coatings, thermistors, and heater/thermostats. The thermal design maintains the core bus and component boundary temperatures between 0 to 40°C for nominal operational modes.

Contact

space@atk.com