01/28/04 -- NAS Supports Aura Spacecraft Checkout
The NAS Division’s networking group recently supported the successful pre-launch checkout of the Aura spacecraft sensor array. The checkout tests provided proof-of-concept for one of the first uses of Quality of Service (QoS) on the NASA Research and Education Network (NREN) testbed, showing that NREN can support the near-real-time demands scientists need.

QoS technologies help maintain network reliability, provide assured bandwidth, and permit protection of data streams. By applying QoS to the tests, the networking team ensured that data sent from the spacecraft was prioritized over any other traffic during testing.

“We supported the checkout so that science teams at GSFC could become comfortable with the data and with the sensors’ behavior before Aura is launched,” says NREN team member David Hartzell. During the tests, high-rate live data (60 to 70 megabits per second—mbit/s) from Aura was captured, converted in real time into ftp format for file transfer, and retransmitted over the NREN wide-area network testbed at Ames Research Center (ARC) to Goddard Space Flight Center (GSFC). The 60- to 70-mbit/s data rate had to be sustained over several five-minute periods per hour so the data could be delivered in near real time. At GSFC, international experts examined the data from the Aura sensors to verify how the instruments will actually operate in space. “It’s not like watching a live video stream,” says Hartzell. “Sensor data is formatted, cleaned up, and then transferred, which takes about five to ten minutes.”

The Aura spacecraft is currently located at Northrup Grumman Space Technology in Redondo Beach, CA. Data ran from there to NASA’s Jet Propulsion Laboratory in Pasadena, then to NREN at Ames Research Center in Mountain View, CA, and finally to GSFC in Greenbelt, Maryland. The networking team provided quality-of-service on the congested link between JPL and ARC to ensure that adequate bandwidth would be available to support the test.

The successful completion of this test was a major milestone in meeting the Aura spacecraft program schedule. The NAS networking team also met a NASA Computing, Networking and Information Systems (CNIS) milestone, demonstrating that QoS works on an application by protecting a data stream while the instrument tests were underway. “NREN’s objective was to verify and show the impact of some of the technologies we are working on,” says Hartzell. “The protection done through QoS proves our ability to support near-real-time science applications over the network. As an additional benefit, the Aura checkout validated the practicality of using Internet protocols (IP) for spacecraft data distribution. It proved that IP can be used to carry varying types of data.”

Other Aura spacecraft checkout tests are currently underway. During these final tests, data will again be prioritized. “We freeze the network configuration during these checkouts,” explains Hartzell. “The network has to remain stable and available so the spacecraft checkout will not be disrupted by a network outage.”

Earth Observing System (EOS) Aura is a NASA mission to study the Earth's ozone, air quality, and climate. EOS Aura is the third in a series of major Earth observing satellites to study the environment and climate change, and is part of NASA's Earth Science Enterprise. The first and second missions, Terra and Aqua, are designed to study the land, oceans, and the Earth's “radiation budget”— the balance between incoming energy from the Sun and outgoing thermal (longwave) and reflected (shortwave) energy from the Earth. The EOS Aura satellite, instruments, launch, and science investigations are managed by GSFC.

For more information about the NAS networking group’s QOS work on Aura, contact David Hartzell at dhartzell@mail.arc.nasa.gov.