Occasionally, the DRL effects the transition from one generation of satellites to another with hardware improvements, but more often new software designs by the DRL staff are needed to upgrade the other ground systems. Further, at approximately 18-month intervals, the DRL holds meetings here at Goddard for representatives of the other direct readout ground stations to communicate information about changes, technologies, policies, and problems that affect the loose confederation of stations. Since the DRL is on the leading edge of direct broadcast and direct readout issues and helps make direct readout ground systems more cost effective, NASA Headquarters funds this effort along with the current EOS Program (in particular, the Terra and Aqua satellites) and its successor, the National Polar-Orbiting Observational Earth Satellite System (NPOESS) Preparatory Project (NPP). The NPP is the vehicle for providing technology infusion into the NPOESS program, which is a tri-agency effort of NASA, the National Oceanic and Atmospheric Administration (NOAA), and the Department of Defense (DOD).

The Terra polar-orbiting satellite, launched in 1999, is continually mapping the Earth’s land surface and measuring heat, light, and the atmosphere to record environmental changes and human impact on climate. The Aqua polar-orbiting satellite, launched in 2002, continuously maps the Earth’s water system to study the effects of heavy weather, hurricanes, tornadoes, snowstorms, etc., providing insight into the water cycle of evaporation and precipitation. NPOESS merges the interests of NASA, NOAA, and DOD into a constellation of three polar-orbiting satellites. Each satellite is designed for a 7-year lifetime and will host 10 to 12 sensor payloads that will provide a wide range of weather and environmental data. The first NPOESS launch is scheduled for 2012.

The DRL can capture data from all NASA EOS satellites and many non-NASA satellites. However, the DRL has NASA mission responsibilities to capture and send level-zero data from the Moderate Resolution Imaging Spectro-radiometer (MODIS) instruments aboard Terra and Aqua to the Goddard Earth Sciences Data and Information Services Center (GES DISC), formerly known as the Goddard Distributed Active Archive Center (DAAC). The importance of level-zero products is that these are raw data directly output from instruments at full resolution, and the raw data provide the basis from which all other data products are produced. For example, MODIS data provides a means for quantifying land surface characteristics such as land cover type, snow cover, surface temperature, leaf area index, and fire occurrences.

While these EOS satellites have their own independent ground system in the EOS Data and Operations System (EDOS), the DRL effort is important to the NASA mission in two respects: First, the DRL data set provides a check and data backup for any problems incurred with EDOS data storage or transmission. For example, the normal route along the EDOS ground system could be corrupted due to some hardware fault, and the DRL route provides an alternative means to obtain good data. Here it must be emphasized that the DRL only captures broadcasts from Terra and Aqua that are directly in the line of sight of its production antenna at Goddard (see Figure 2). The extreme range of this local line of sight extends approximately 2,000 km east and west and 3,000 km north and south of the antenna. Of course, instruments from these satellites are taking data constantly in a downward-looking mode, and data can be missed outside of the DRL local area, i.e., the East Coast vicinity of the United States. Second, the DRL provides a service to the EOS mission in these cases of missing data by locating and pulling good data from any of the 120 other direct readout ground stations and supplying it to the GES DISC.

Providing data to the GES DISC is an important mission-related secondary activity of the DRL.  The primary activity of the DRL will continue to be influencing cost-effective hardware designs, both on-board the satellite and the ground segment, and providing data system software tools, and the science instrument processing algorithms.  Thus, this primary role of the DRL insures that a direct readout ground station will be able to cost-effectively acquire and process EOS and NPP/NPOESS satellite data for the benefit of real-time Earth remote sensing data users.  The cost-effectiveness of direct readout ground systems has vastly improved in the last decade, with costs dropping from millions of dollars to thousands of dollars. The cost driver for any direct readout ground station continues to be the antenna. For an L-band system, the present cost is about $15,000, and for an X-band system, the cost is $120,000. The cost difference between the two systems derives from the more critical tolerances in fabrication of the more exacting surface for the higher-frequency antenna. The DRL and Goddard continue to work with the commercial sector to bring these costs down by providing data processing tools and algorithms that make the hardware more useful, which, in turn, creates a larger user base, which then leads to a larger production volume and, hence, lower costs. Thus, the bottom line is that the cost-effective services of the DRL help ensure that end users will continue to invest resources into having their own direct readout systems to acquire, process, and utilize Earth satellite data in near real time.