Unmanned System Data Protocol and Format

In September 2007 the United States Air Force (USAF) transferred to pre-production Global Hawk aircraft to the National Aeronautics and Space Administration (NASA) (NASA Center for AeroSpace Information, & United States. National Aeronautics and Space Administration, 2009b).  This came to fruition due to a failed plans for NASA to uses USAF aircraft, this was because the Department of Defense (DoD) priorities dictated otherwise (NASA Center for AeroSpace Information, & United States. National Aeronautics and Space Administration, 2008b).  This paper will examine the communications payloads onboard, data format, protocols, and storage methods used to make this platform effective and functional. Additionally, onboard sensors will be examined and the overall data strategy, as well as possible improvements.

The NASA Global Hawk communication payload consists of: two UHF/LOS links, two Iridium link, and one Inmarsat link which provide command and control (C2) communications; two iridium links for communications with Air Traffic Control (ATC); and  six Iridium links for Payload C2 and health status (NASA Center for AeroSpace Information, & United States. National Aeronautics and Space Administration, 2009b).  These communications payloads are exemplified in FIGURE 1.

Figure 1.  Concept of operations for NASA’s Global Hawk communications payloads. Courtesy of NASA Center for AeroSpace Information, & United States. National Aeronautics and Space Administration, 2009b.

            The NASA Global Hawk can fly missions of up to 30 hours, and for this reason status packet can be monitored by the Mission Scientist and Payload Operator so that they can have situational awareness (NASA Center for AeroSpace Information, & United States. National Aeronautics and Space Administration, 2008a).  These packet are in a Comma-separated values American Standard Code for Information Intercahnge (CSV ASCII) format which is similar to Interagency Working Group standard format number 1 (IWG1) (NASA Center for AeroSpace Information, & United States. National Aeronautics and Space Administration, 2008a).  In the CSV ASCII format, “a leading identifier, with comma separated values, and with the first value being a timestamp” (NASA Center for AeroSpace Information, & United States. National Aeronautics and Space Administration, 2008a).  Additional parameters include the instrument status code as the second parameter and there shall not be more than 16 total parameters (NASA Center for AeroSpace Information, & United States. National Aeronautics and Space Administration, 2008a). 

The Link Module system is the on-board file serve and data base that instruments can use for back up storage of data and caching of flight data request (NASA Center for AeroSpace Information, & United States. National Aeronautics and Space Administration, 2008a).  Additionally, wide band satellite communications (SATCOM) is available when within the geographical footprint and can provide from 56 Kbps and up to 50 Mbps of service (NASA Center for AeroSpace Information, & United States. National Aeronautics and Space Administration, 2008a). 

The NASA Global Hawk sensor suite can be changed to accommodate different sensors for different missions (NASA Center for AeroSpace Information, & United States. National Aeronautics and Space Administration, 2014).  For example, in 2011 a National Oceanic and Atmospheric Administration (NOAA) sponsored flight called for the deployment of dropsondes (NASA Center for AeroSpace Information, & United States. National Aeronautics and Space Administration, 2014).  A dropsonde is a tube about the size of a paper towel roll and transmits temperature and humidity as it drifts and transmits this information to include its GPS location (Newman, 2015).  In 2014 a LIDAR instrument was fitted to the NASA Global Hawk, both a real-time and stored product were available to the ground users (McGill et al., 2014).  As a default practice, images were transferred and saved every five minutes during flight (McGill et al., 2014).

NASA’s Global Hawk sensor payload can range depending on the mission and the customer’s requirements.  Onboard storage will usually give better fidelity in a case where large amounts of data are unable to be transmitted or have to be converted to a lower fidelity before being transmitted.  Sensors are continually evolving, for example the ARGUS Eye can collect one million terabytes of high definition video a day which equates to 5,000 hours of video (Rise of the Drone, 2013).  This creates a need for onboard storage or more data links to stream information.  Data links tend to come a premium because there is only so much of the frequency spectrum that can be used and there are lots of every day devices that use these frequencies as well, such as cell phones and Wi-Fi.  So, it would seem most practical to keep data on board and only transmit when requested by the ground station.

NASA’s Global Hawk is a highly capable asset and can be reconfigured to meet the mission requirements set forth by the customer.  However, the Global Hawk faces an issue many unmanned platforms will begin to see, it is the fact that sensor technologies are moving faster than the ability to process, store, and transmit the data collected.

References

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