[meteorite-list] Rosetta's Pioneering Philae Comet Lander Reactivated

[Ron Baalke]

http://www.spaceflightnow.com/rosetta/140401philae/
 
Rosetta's pioneering Philae comet lander reactivated
BY STEPHEN CLARK
SPACEFLIGHT NOW
April 1, 2014

Since the Rosetta spacecraft emerged from hibernation in January, engineers 
have checked the probe's systems and found them in good condition, according 
to Andrea Accomazzo, Rosetta's spacecraft operations manager at the European 
Space Agency.

Rosetta is heading toward an August rendezvous with Comet 67P/Churyumov-Gerasimenko, 
an inner solar system comet that completes one circuit of the sun every 
six-and-a-half years.

Ground teams started activating Rosetta's science instruments March 17, 
successfully switching on the spacecraft's primary science camera, ultraviolet 
spectrometer, and a plasma sensor suite to study the environment around 
the comet.

On Friday, the $1.7 billion mission's German-built Philae lander woke 
up and radioed Earth.

"Philae is operational and ready for the next few months," said Stephan 
Ulamec, Philae project manager at DLR, the German space agency.

Philae will be ejected from the Rosetta mothership in November to latch 
itself onto the comet's icy surface with harpoons and screws. The lander 
has its own suite of science instrumentation to take the first-ever photos 
and measurements from a comet's surface.

Engineers plan a four-week commissioning phase for Philae to check on 
its health and activate the lander's 10 instruments.

"We will analyse this data thoroughly, so we can find out whether Philae 
has survived the long flight and hibernation intact," Ulamec said in a 
DLR press release.

Before Friday, controllers last received data from Philae on June 8, 2011, 
when Rosetta entered hibernation. Since Rosetta woke up in January, the 
craft sent back preliminary temperature measurements from Philae.

The first data packets from Philae arrived on Earth at 1440 GMT (10:40 
a.m. EDT) Friday through a NASA tracking antenna in California, which 
fed the telemetry to the lander's control center in Germany.

Philae's 10 instruments will be activated and tested throughout April. 
By May, all of the mission's science payloads will be commissioned, including 
the 11 instruments aboard the Rosetta mothership.

So far, Rosetta's scientific camera has finished its round of testing 
since the spacecraft woke up in January. The Optical, Spectroscopic and 
Infrared Remote Imaging System, developed by the Max Planck Institute 
for Solar System Research in Germany, took the first pictures of the comet 
since hibernation on March 20 and 21.

"Finally seeing our target after a 10 year journey through space is an 
incredible feeling," said Holger Sierks, OSIRIS principal investigator 
at the Max Planck Institute. "These first images taken from such a huge 
distance show us that OSIRIS is ready for the upcoming adventure."

Churyumov-Gerasimenko was about 5 million kilometers, or 3.1 million miles, 
from Rosetta when the pictures were taken earlier this month.

The rest of Rosetta's instruments are still being tested.

A series of engine burns in May will adjust Rosetta's course toward the 
comet, burning much of the spacecraft's remaining fuel. Rosetta is now 
on a trajectory to miss the comet by approximately 50,000 kilometers, 
or about 31,000 miles.

The trajectory correction maneuvers in May will guide Rosetta within 100 
kilometers, or about 60 miles, of Churyumov-Gerasimenko by the first week 
of August, according to ESA.

Officials have penciled in Philae's landing on Churyumov-Gerasimenko for 
Nov. 11, but the date could be adjusted a few days based on the probe's 
landing site and conditions around the comet.

Philae will operate for at least two days on the comet, and it carries 
solar arrays to recharge its battery if comet's unpredictable dust environment 
cooperates.

"Landing on the surface is the cherry on the icing on the cake for the 
Rosetta mission on top of all the great science that will be done by the 
orbiter in 2014 and 2015," said Matt Taylor, Rosetta's project scientist, 
in a blog post on ESA's website. "A good chunk of this year will be spent 
identifying where we will land, but also taking vital measurements of 
the comet before it becomes highly active. No one has ever attempted this 
before and we are very excited about the challenge!"

One of Philae's instruments will drill into the comet's surface, collect 
a sample and feed it into an on-board oven for analysis.

Scientists do not know what environment awaits Rosetta and Philae at the 
comet.

Controllers will cautiously approach Churyumov-Gerasimenko with Rosetta, 
taking cues on how to navigate around the comet based on the amount of 
debris observed by the spacecraft's two main cameras.

The flexible approach allows officials to keep a safe distance from the 
comet if the ice and dust are deemed too hazardous.

Rosetta will follow the comet for at least a year while it makes its closest 
approach to the sun, watching Churyumov-Gerasimenko "wake up" as sunlight 
and heating trigger the comet's volatile jets of water vapor and gas.

Scientists are eager to better understand comets because they may have 
seeded Earth with water and the building blocks of life soon after the 
genesis of the solar system.

"They are time capsules," said Mark McCaughrean, senior advisor in ESA's 
science and robotic exploration directorate, in a press conference in 
December. "They are remnants of the birth of the solar system. They go 
back to the beginning of the solar system more than 4.6 billion years 
ago."