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Internet for the Aliens
Internet for the aliens? Well, not quite. Using the Deep Impact spacecraft from a previous mission, NASA is trying to create an "interplanetary Internet," or a network similar to the structure of our terrestrial Internet so that instruments may talk to each other from millions of miles away. Deep Impact was launched in January 2005 and released an impactor that slammed itself into comet Tempel 1 in order to discover more about the chemistry of comets. Now the craft hosts a combination of two separate investigations, EPOCh and DIXI, so it has been renamed EPOXI. Sometimes, however, the NASA scientists still refer to the craft as Deep Impact.
EPOCh (Extrasolar Planet Observations and Characterization), which lasted from January through August of 2008, used a high-resolution instrument (HRI) to examine stars with giant, orbiting planets. The HRI also served as a photometer, measuring the light emitted from the stars to help detect the extrasolar planets. In addition to its study of these planets, EPOCh observed the earth in a series of three flybys.
DIXI (Deep Impact Extended Investigation) is an extension of the original mission, Deep Impact, to comet Tempel 1--now it is headed for Hartley 2. DIXI will help scientists to continue investigating the origins of the solar system and how it has evolved. The extended mission, cost relatively little, $40 million, compared to other projects because NASA was able to reuse the Deep Impact craft. So, EPOXI is a good example of recycling.
EPOXI is simply one of ten nodes forming the interplanetary Internet, which was successfully tested on November 18, 2008. During the test, EPOXI simulated a craft stationed on Mars, and NASA sent images between the earth and the spacecraft a few times.
The problem with an interplanetary network is that the large distances between spacecraft causes delays, disruptions, and disconnections during transmission. Thus, software known as Disruption-Tolerant Networking (DTN) is required. Even though this is troublesome, DTN comes with a benefit: even if there is an interruption in transmission, the data will eventually reach its destination. This is because each network node stores the information, then forwards it when the destination path is finally open again. This network will allow dependable communication between spacecraft, astronauts on the moon, and Earth.
EPOXI will be in hibernation throughout 2009, but it will wake up again in the fall of 2010 as it approaches the comet, Hartley 2.
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