NOAA KLM User's Guide
The Data Collection System/2 (DCS/2) is one of the environmental monitoring systems flown on the NOAA KLM and NOAA-N spacecraft. The DCS/2 assists NOAA in its overall environmental mission and in support of the Global Atmospheric Research Program (GARP). It has approximately 2000 environmental platforms located around the Earth to measure such environmental factors as temperature, pressure, and currents. Some of these platforms are immersed in a moving fluid, such as the ocean and the atmosphere. These moving platforms, buoys and balloons, provide additional environmental information on velocity and direction of the ocean and wind currents.
The DCS/2 receives information from these fixed and moving environmental platforms and processes and transfers the data for storage by the spacecraft tape recorders. These stored data are transmitted to a NOAA ground station during station contact. The ground station records and transmits the DCS/2 data to CNES and to Service ARGOS in Landover, Maryland. CNES is the responsible manufacturing, system engineering and data distribution agency for the DCS/2.
The DCS/2 is comprised of three units: the Receiving and Power Unit (RPU) and two Signal Processor Units (SPU-A and SPU-B). The platforms transmit data to the DCS/2 at a carrier frequency of 401.650 MHz, digital biphase format at 400 bps. The DCS/2 demodulates this signal and determines the carrier frequency and relative time of each transmission. This data is processed, formatted, and transferred to the TIROS Information Processor (TIP). The following paragraphs describe how the processing occurs in each of the DCS/2 units.
The receiver linearly converts the incoming signal by means of two translations to an intermediate frequency which is applied to the input of the search unit and to the Data Recovery Units (DRUs). The search unit is basically a spectrum analyzer which uses a Fast Fourier Transform to cover the 80 kHz operating frequency range.
The control unit (CU) sequentially scans the eight search unit channels. It makes a binary estimate of both the signal level and frequency. These two digital words are stored in the CU and are used for the assignment of a DRU to a particular receiver output signal.
The DRU is comprised of three sections: (1) phase-lock loop, (2) bit synchronizer, and (3) Doppler counter and formatter. The eight DRUs perform the following signal functions: acquisition of the carrier, signal demodulation, bit synchronization, frame synchronization, Doppler counting, decommutation and formatting of the data.
The telemetry formatter interrogates the buffer in the DRUs. When the buffer is full, the encoder sends a command to shift the 24 bits into memory. When the data transfer signal from the TIP is received by the encoder, it will transfer the data out of memory to the TIP.
Power for the DCS/2 is supplied by the spacecraft +28 V main power bus. This voltage is converted by the power unit to four levels; +5.0, +12, -12, and -15 V. Regulation and current limitation is provided for each of these DCS buses. The command unit consists of seven relays which perform the ON/OFF functions for the DCS/2. The Control Interface Unit (CIU) sends pulse commands which control these relays. The command unit sends back to the TIP 14 status bits and six analog bits.
The DCS/2 has no on-orbit calibration requirements.
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