NASA, Johnson Space Center, BE13, Houston, TX

30 -- GLOBAL POSITIONING SYSTEM (GPS) SIGNAL GENERATOR SOL 9BE1318526P DUE 062595 POC YOLANDE HARDEN, Tel:713-483-9953 Contracting Officer:JOHN TRAHAN, Tel:713-483-0543 NASA Johnson Space Center and Goddard Space Flight Center both have requirements for a Global Positioning System (GPS) Signal Generator. The signal generators will be used to perform GPS navigational roles such as: navigation state, relative state, differential state, attitude determin- tion. The signal generators should provide a minimum of 10 L1 channels on each of the 4 RF outputs. The signal generators will be used in an integrated Guidance, Navigation and Control hardware simulation setting and the need for external inputs to drive the signal generators environ- ment model is a required capability. The signal produced by the signal generator is required to have user defined multipath error model parameters. Selective availability, Ionospheric range biases, Troposheric range bias errors must also be produced as part of the signal generator output. Two seperate contracts shall be awarded, one for each center. This procurement shall be implemented according to the MidRange procurement procedures as approved by the Office of Federal Procurement Policy on 4/16/93. --GPS Signal Generator Requirements: A. Signal Generator Functional Requirements - the GPS signal generator shall support the following functions: 1) navigation state determination; 2) attitude determination; 3) differential state determination; 4) relative state determination. B. Operations Requirements: - 1) the signal generator (SG) shall have 10 channels of RF signal output; 2) the SG shall have 4 RF outputs; 3) the SG shall provide both pseudorange and differential phase measurements that are consistent with multiple antenna locations for independent trajectories; 4) each channel shall have 2 outputs -- a) the first output of each channel shall produce carrier waves at the 1575.42 MHz. Super- imposed on the carrier wave shall be pseudo random noise codes as a binary biphase modulation at 1.023 MHz and a realistic GPS binary message added to the binary navigation biphase modulation at 50 bits per second (navigation message), b) the second output of each channel shall be a corruption first output of each channel due to the user specified multi- path environment; 5) the SG shall include a real time operating system computer (workstation); 6) the SG workstation shall have adequate hard drive space to provide: a) 9 hours of continuous differential phase testing, b) logging of position, velocity, acceleration, attitude, and time; 7) the SG shall set the following initial parameters via the work- station for 2 independently generated trajectories (i.e. to support relative and differential GPS): a) all GPS almanac parameters - Almanac from Coast Guard Bulletin Board, b) all GPS emphermis parameters, c) receivers/processers initial state -- position, velocity, acceleration attitude, body angular rate, body angular acceleration, d) initial time, e) dynamics model - gravity model, drag model, inertia tensor; 8)the receiver/processor initial state shall be input to the workstation in either Keplerian element or state vector format; 9) the operator shall have the option of having the position and attitude propagated from an initial state for the duration of the test; 10) the SG shall accept the following inputs into the SG environment model from an external computer at a rate greater than or equal to 1 Hz: a) receiver/processor state - position, velocity, acceleration, attitude, body angular rate, body angular acceleration; 11) the operator shall have the ability to execute scripted runs from an external computer; 12) the SG operators shall be able to script the followings capabilities during the mission simulation: a) failure of any GPS satellite vehicles (SV), b) antenna placement, beamwidth, orientation, and gain pattern -- 1) the antenna gain pattern shall be a function of the relative azimuth and elevation angles between the antenna boresight and relevant GPS satellite, 2) the gain pattern shall be present in the output of each channel, c) the SG shall give the operator the ability to change the attenuation on the signal as well as changing the attenuation on the noise; 13) the SG shall produce the following GPS signal propagation errors: a) simulated selective availability, b) Ionospheric range biases, c) Tropospheric range biases, d) Multipath- 1) SG shall simulate direct and indirect (multipath) signals based on input geometry, 2) applicable to both errors to pseudo- range and carrier phase measurement, 3) SG shall have the capability to accept as input a file containing a function of the azimuth and elevation of the GPS satellite; 14) the operator shall have the option of turning off and on the GPS signal propagation errors. --One signal generator is required for each center. --NASA Johnson Space Center and NASA Goddard Space Flight Center --Delivery is required by December 1, 1995. 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