A system of interface electronic circuitry that includes a data packetizer and a data depacketizer has been developed to enable the downlinking of both standard- and high-definition television (SDTV and HDTV) signals from a space shuttle or the International Space Station. The packetizer accepts electronic input of a stream of data from a commercial-off-the-shelf SDTV or HDTV compression encoder that operates according to the MPEG-2 (Moving Pictures Experts Group) standard and outputs the DVB ASI (Digital Video Broadcast Asynchronous Serial Interface) format. The packetizer converts the input stream to an output stream of data packets that conforms to a standard of the Consultative Committee for Space Data Systems (CCSDS) and is compatible with either the Space Station High Rate Frame Map (HRFM) or the space shuttle downlink data multiplexer. The packetizer output circuitry includes a transparent asynchronous transceiver interface (TAXI), which transmits the packets to the downlink data multiplexer or HRFM via a fiber-optic link. The depacketizer is implemented as a printed-circuit board that is plugged into a ground system computer. The ground system displays health and status of the flight system as well as providing the recovered MPEG-2 video for ground use.
This work was done by S. Douglas Holland of Johnson Space Center. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Electronic Components and Systems category.