NASA today said it had successfully tested its deep space communications network modeled on the Internet. Specifically the space agency used its Disruption-Tolerant Networking, or DTN technology to send dozens of space images to and from a NASA's Epoxi spacecraft located about 20 million miles from Earth.
Epoxi is on a mission to encounter Comet Hartley 2 in two years. NASA employed 10 nodes on this early interplanetary network. One is the Epoxi spacecraft and the other nine, which are on the ground at NASA's Jet Propulsion Laboratory in Pasadena, Calif, simulate Mars landers, orbiters and ground mission-operations centers, NASA said.
NASA's DSN is made up of myriad systems. It includes an international network of antennas that supports interplanetary spacecraft missions and radio and radar astronomy observations for the exploration of the solar system and the universe. The DSN currently includes of three deep-space communications facilities placed approximately 120 degrees apart around the world: at Goldstone, in California's Mojave Desert; near Madrid, Spain; and near Canberra, Australia. This placement permits constant observation of spacecraft as the Earth rotates, and helps to make the DSN the largest and most sensitive scientific telecommunications system in the world, NASA said.
NASA and Vint Cerf, a vice president at Google partnered 10 years ago to develop the protocols for DSN, NASA said.
In a white paper, NASA last month said that its Deep Space Network (DSN) will be modified to meet new performance and interoperability requirements for its planned moon shots. NASA stated: A small constellation of Lunar Relay Satellites (LRS) will be placed into orbits with long term stability that provide periodic coverage of the entire surface of the Moon as well as Low Lunar Orbit (LLO). Two LRSs provide periodic coverage of the entire Moon for sortie support. Medium and high rate links will be provided between the LRS and Lunar Communication Terminals (LCT) at the Outpost. Lunar surface communications will use commercial IP network technologies running for interplanetary communications based on an open, standards-based architecture. S- and Ka-bands are employed for both the Earth-Moon long haul links and the lunar orbit-to-surface links. S-, K- and Ka- bands are used for primary surface-to-surface links while S-band is used for contingency voice channels. Standards will be coordinated with other national space agencies to ensure international interoperability.
NASA said the Interplanetary Internet must be tough enough to withstand delays, disruptions and disconnections in space. Glitches can happen when a spacecraft moves behind a planet, or when solar storms and long communication delays occur. The delay in sending or receiving data from Mars takes between three-and-a-half to 20 minutes at the speed of light, NASA said.
Unlike TCP/IP on Earth, the DTN does not assume a continuous end-to-end connection, NASA said. In its design, if a destination path cannot be found, the data packets are not discarded. Instead, each network node keeps the information as long as necessary until it can communicate safely with another node. This store-and-forward method means information does not get lost when no immediate path to the destination exists. Eventually, the information is delivered to the end station.
NASA said it tested the system for a month as part of a series of planned demonstrations to qualify the technology for use on a variety of upcoming space missions. In the next round of testing, a NASA-wide demonstration using new DTN software loaded on board the International Space Station is scheduled to begin next summer, the agency said.
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