Spaceflight Now: Breaking News

Saturn-bound Huygens probe takes mid-course exam
Posted: July 30, 2000

  Huygens deploy
Artist's concept of Huygens descent into Titan's atmosphere. Photo: ESA
The 6th Huygens in-flight checkout was executed as planned on Friday from 16:00 GMT to 19:28 GMT. Cassini/Huygens was 685 million kilometer away from Earth on its way to Jupiter. The Cassini telemetry data were received via the Goldstone Deep Space Network antenna DSS-15 and routed to JPL. The Huygens data were stripped out at JPL and sent for evaluation to the Huygens Probe Operations Centre (HPOC) at ESOC, Darmstadt, Germany.

The first data arrived at ESOC at 16:39 GMT as it took 38 minutes for the radio signal to travel from Cassini/Huygens to Earth at the speed of light, and less than 1 min for JPL to pre-process and forward them to HPOC. The first signs of life from Huygens were acclaimed with some relief at HPOC.

"A Huygens checkout will never be a routine activity. Itıs the end step of several months of careful preparatory work for the Huygens Flight Operations Team. There is always some emotion when we hear from our little Probe which is now so far from us," said Jean-Pierre Lebreton, the Huygens Project Scientist.

A preliminary evaluation of the data indicates that the checkout was nominally executed and that the Probe and its payload performed as expected. The data were pre-processed at HPOC and sent to the experimenter teams for a detailed evaluation. The results of the checkout will be reviewed in details at HPOC in mid-October.

Cassini location plot. Photo: NASA/JPL
The position of the spacecraft at the time of the checkout is illustrated in the above image, which was composed by using the Solar System Simulator tool from JPL.

Cassini was pointing its High Gain Antenna (HGA) at Earth during the checkout and the Sun was about 10 degrees away from the antenna boresight (axis).

As expected the radio noise level at the input of the Huygens receivers was low, at about the same level as during the previous checkout. Hence, the Huygens receivers were operating in a very good signal-to-noise ratio environment. This is confirmed by the high AGC level returned in the Huygens telemetry.