NASA/GSFC, CODE 214.4, GREENBELT, MD 20771

99 -- MIDEX SPACECRAFT COMPONENTS POC JOAN W. TOMASELLO, CONTRACTING OFFICER, (301)286-6535. 99 Goddard Space Flight Center (GSFC) is interested in surveying possible sources of spacecraft components for upcoming NASA missions, including the MIDEX series of Explorer spacecraft. MIDEX is NASA's new medium-sized class spacecraft program, designed to provide frequent, high-end space science missions at the lowest possible cost. In order to minimize MIDEX development costs, GSFC is planning on procuring standard products which have been developed for the commercial market. To that end, GSFC is currently developing component specifications which will allow vendors to propose existing products rather than requiring new developments. It is our goal that these specifications can be used over a wide variety of missions, by a variety of spacecraft developers. This will encourage the development of more open space system architectures. The components listed below were selected to envelope the requirements of several possible NASA missions, but do not necessarily represent the requirements of any singular mission. They are limited to Attitude Determination and Control, and Power subsystem components at this time. Vendors should use the performance list as a set of guidelines with which to match their closest standard product, rather than a set of minimum requirements. Performance guidelines have been determined from the advertisd capabilities of the MIDEX spacecraft. Vendors are asked to respond with information describing capabilities, experience, past performance, and qualifications, on one or more of the components listed below. Vendors are strongly encouraged to provide in their capability statement information about other standard products which do not necessarily fit the performance category listed below, but could be used for other missions. Vendors are not expected to provide information about the entire list, only those components for which they consider themselves potential sources. Information about a vendor's internal product quality system is also appreciated. INERTIAL REFERENCE UNIT: Provide information about rate sensing units (either single axis or multiple axis packages) that provide integrated rate information over a non-proprietary data interface (preferably employing a standard data interface such as MIL-STD-1773, ML-STD-1553 or RS-422). Appropriate performance includes output quantization less than 0.1 arcsecond, and angle random walk less than 0.01 degrees/root hour. In order to fully cover the range of possible missions, information about IRU's that exceed this performance class are also encouraged to respond. MOMENTUM EXCHANGE DEVICES: Provide information about momentum storage devices (either momentum or reaction wheels) that can provide between 10 and 20 Newton-meter-seconds of momentum storage and 0.08 Newton-meters of reaction torque. The data interface must provide an interface for torque commands and tachometer data. The wheel may be an integrated unit or be divided into separate wheel and electronic assemblies. Information about wheels that provide different torque or momentum storage capabilities is strongly encouraged, but not required. DIGITAL SUN SENSORS: Provide information about digital sun sensors that fit into any of the following performance categories: a spinning spacecraft sun sensor (used to provide attitude reference in the transverse axis of a spinning spacecraft), a digital sun sensor (used for sun knowledge better than 0.5 degrees over a 100 degree x 100 degree FOV), and a fine sun sensor (used for knowledge better than 2 arcminutes over a 50 degree x 50 degree FOV). EARTH SENSORS: Provide information about earth sensors that fit into any of the following categories: horizon crossing indicators (used on spinning spacecraft to provide an Earth Reference), GEO sensors (FOV scaled to provide attitude reference at Geosynchronous orbit), and LEO sensors (used for knowledge of the nadir vector to within 0.5 degrees). Sensors which exceed the performance listed are encouraged to participate in order to correctly assess the capabilities of the market. STELLAR SENSORS: Provide information about standard stellar sensors and star trackers that can provide inertial attitude reference to better than 1 arcminute. Sensors can either provide a quaternion output that represents the projection of the boresight with respect to an inertial coordinate system or provide raw data which provides star positions relative to the boresight. Sensor data should be provided over a non-proprietary data interface (preferably employing a standard data interface such as MIL-STD-1773, MIL-STD-1553 or RS-422). Vendors are encouraged to discuss capabilities beyond those requested here, and to discuss tradeoffs beteen system performance and unit cost. GPS RECEIVERS: Provide information about GPS receiver networks that can provide a correlated time reference and orbital position accurate to within 500 meters absolute. Sensor data should be provided over a non-proprietary data interface (preferably employing a standard data interface such as MIL-STD-1773, MIL-STD-1553 or RS-422). Vendors are also encouraged to discuss attitude determination via GPS, in addition to the requirements listed above. SOLAR CELL ARRAY BUILDING BLOCK DESIGNS: Provide information about qualified solar array segments for a direct energy transfer (DET) system with an unregulated 28 volt (28+/-7) battery bus. The intent is to reuse existing designs, tooling, materials, procedures, and qualification of the basic building blocks of the solar array. Information is requested regarding array segments from single strings up to approximately 1000W BOL, 28V, 28xC, AMO sized sections. The information requested is: string configuration, cell type, coverglass type and thickness, overall dimensions, substrate requirements - if any, stringing arrangement for multiple string segments, temperature range and cycles of qualification and original mission, radiation degradation curves and design life. Vendors are encouraged to include a large number of configurations to maximize the likelihood that reuse can occur. BATTERY DESIGNS: Provide information about qualified long-life battery options. Information is requested for NiCd and NiH2 types of 22 cell configurations with amp-hour capacities up to approximately 50 AHr. For the NiH2 types, Individual, Common and Single Pressure Vessal configurations are being considered. Vendors are encouraged to include information on various mechanical configurations to minimize redesign efforts. Requested information is: battery type, weight, overall dimensions, capacity, qualification and flight history including number of cycles, depth of discharge and temperatures. This is not a Request for Proposal and should not be construed as a committment by the government. Rather, information gathered by this survey will be used to validate specifications which may be required for procurements to take place later this fiscal year. Draft copies of these RFPs may be made available to potential sources for review and comment in the upcoming months. Prospective sources should submit the required data within 20 days of the dat of this publication. All interested parties to the Sources Sought synopsis need not submit another request. Electronic versions of the documents will be provided on the World Wide Web at http://genesis.gsfc.nasa.gov/procure.htm, and by anonymous ftp to genesis.gsfc.nasa.gov/public/solicita. (0284)

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