NASA's Pluto probe begins intensive data downlink phase

After its historic flyby of Pluto in July, NASA's New Horizons spacecraft has just started intensive downlinking of the tens of gigabits of data it collected and stored on its digital recorders.

The process moved into high gear on September 5, with the entire downlink taking about one year to complete.

"This is what we came for - these images, spectra and other data types that are going to help us understand the origin and the evolution of the Pluto system for the first time," said New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute (SwRI) in Boulder, Colorado.

"And what's coming is not just the remaining 95% of the data that's still aboard the spacecraft - it's the best datasets, the highest-resolution images and spectra, the most important atmospheric datasets, and more. It's a treasure trove," said Stern.

Even moving at light speed, the radio signals from New Horizons containing data need more than four and a half hours to cover the 3 billion miles to reach Earth.

As a flyby mission, New Horizons was designed to gather as much information as it could, as quickly as it could, as it sped past Pluto and its family of moons - then store its wealth of data to its digital recorders for later transmission to Earth.

Since late July, New Horizons has only been sending back lower data-rate information collected by the energetic particle, solar wind and space dust instruments.

The pace picked up considerably on September 5 as it resumed sending flyby images and other data.

During the data downlink phase, the spacecraft transmits science and operations data to NASA's Deep Space Network (DSN) of antenna stations, which also provide services to other missions, like Voyager.

The spacecraft's distance from Earth slows communication rates, especially compared to rates offered by today's high-speed Internet providers.

With New Horizons past Pluto, the typical downlink rate is approximately 1-4 kilobits per second, depending on how the data is sent and which DSN antenna is receiving it.

"The New Horizons mission has required patience for many years, but from the small amount of data we saw around the Pluto flyby, we know the results to come will be well worth the wait," said Hal Weaver, New Horizons project scientist from the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland.