Two military satellites recently exchanged more than 200 gigabits of data over a distance of about 100 kilometers using laser communication in space. Satellites generally do not communicate directly with each other. Instead, they use radio signals to transfer data down to a ground station on Earth, which then relays this data to another satellite. Optical terminals between satellites are considered to be faster and more secure. The two satellites, named Able and Baker, were launched last summer by the U.S. Defense Advanced Research Projects Agency as part of its Blackjack project.

A much slower data transfer takes place under more challenging conditions when communicating with humanity's outpost beyond our solar system. NASA engineers are investigating anomalous telemetry data produced by the venerable space probe Voyager 1. They are now trying to debug the probe, a formidable task as data flows from Voyager at 160 bits per second, and signals take 20 hours and 33 minutes to reach the probe. A Wednesday announcment states that the probe is operating normally, receiving and executing commands from Earth, and still doing science and phoning home with data. But Voyager 1’s attitude articulation and control system (AACS), that helps point the probe’s antenna towards Earth, does not currently reflect what’s actually happening onboard. NASA says the AACS data may appear to be randomly generated, or does not reflect any possible state the AACS could be in. The good news is that the craft is still doing fine. It’s not needed to enter safe mode and its signal is still strong, so it appears the main antenna is properly aligned even if system data suggests otherwise.

AMSAT - http://www.amsat.org/