• INTERNET TECHNOLOGY FOR FUTURE SPACE MISSIONS

      Rash, James; Hogie, Keith; Casasanta, Ralph; NASA; Computer Sciences Corporation (International Foundation for Telemetering, 2002-10)
      Ongoing work at National Aeronautics and Space Administration Goddard Space Flight Center (NASA/GSFC), seeks to apply standard Internet applications and protocols to meet the technology challenge of future satellite missions. Internet protocols and technologies are under study as a future means to provide seamless dynamic communication among heterogeneous instruments, spacecraft, ground stations, constellations of spacecraft, and science investigators. The primary objective is to design and demonstrate in the laboratory the automated end-to-end transport of files in a simulated dynamic space environment using off-the-shelf, low-cost, commodity-level standard applications and protocols. The demonstrated functions and capabilities will become increasingly significant in the years to come as both earth and space science missions fly more sensors and the present labor-intensive, mission-specific techniques for processing and routing data become prohibitively. This paper describes how an IP-based communication architecture can support all existing operations concepts and how it will enable some new and complex communication and science concepts. The authors identify specific end-to-end data flows from the instruments to the control centers and scientists, and then describe how each data flow can be supported using standard Internet protocols and applications. The scenarios include normal data downlink and command uplink as well as recovery scenarios for both onboard and ground failures. The scenarios are based on an Earth orbiting spacecraft with downlink data rates from 300 Kbps to 4 Mbps. Included examples are based on designs currently being investigated for potential use by the Global Precipitation Measurement (GPM) mission.
    • A STANDARD LINK-LAYER PROTOCOL FOR SPACE MISSION COMMUNICATIONS

      Parise, Ron; Hogie, Keith; Criscuolo, Ed; Schnurr, Rick; Wesdock, John; Burns, Mark; Computer Sciences Corp; NASA; ITT Industries (International Foundation for Telemetering, 2002-10)
      A necessary step for using Internet Protocols in space is to establish the basic link-layer framing protocol for delivering Internet datagrams over satellite RF links. This paper discusses the low-level data link issues related to using the ISO standard High-level Data Link Control (HDLC) protocol to support spacecraft communications. A major driver for using HDLC is its very wide usage in the Internet today and the large amount of commercially available network equipment and test equipment. The results of a high-fidelity link simulation using HDLC are presented along with results of tests performed in 2000-2001 using Internet protocols over HDLC on the UoSAT-12 spacecraft. A rationale is provided for the selection of HDLC/Frame-Relay framing along with the IETF multi-protocol encapsulation. It also discusses the historical usage of HDLC on over 70 satellite missions. The paper also describes how HDLC relates to various applications of forward-error-correction (FEC) coding techniques, such as convolutional coding and Reed-Solomon. It describes approaches for using these techniques in ways that are independent of the protocols used at the data link layer and above. It covers issues primarily related to layer 2 (Data Link) and its relationship to layer 1 (Physical). It does not cover layer 3 (Network) and above.