As frenzied anticipation mounts worldwide for history’s audacious first attempt to land on a comet, Europe’s Rosetta orbiter locked on to the bizarre body and captured a bull’s-eye view of the utterly alien “Agilkia” landing site.
The orbiter’s navcam camera mosaic showing Agilkia above gives a rather vivid indication of the daunting task that lies ahead in just two days’ time for the mission team and the first-of-its-kind space probe.
The Rosetta orbiter is scheduled to deploy the small Philae lander on Nov. 12, for the daring attempt at a safe touchdown on a comet for the first time in human history.
Philae must endure “seven hours of terror” between departure from Rosetta and touchdown on Agilkia.
Philae is being targeted to the “head” of comet 67P/Churyumov–Gerasimenko, an extremely odd, two-lobed celestial body stemming from the origin of our Solar System.
The Rosetta/Philae mission was designed and built by the European Space Agency (ESA) with significant participation from NASA in the form of several science instruments.
Rosetta mission managers announced today, Nov. 10, that all systems are currently “GO” for Rosetta to dispatch Philae on Wednesday.
“The Rosetta spacecraft and Philae lander are in great shape,” said Flight Director Andrea Accomazzo at a media briefing today at the European Space Operations Center (ESOC) in Darmstadt, Germany.
On Nov. 12, Rosetta is scheduled to release Philae at a slightly revised time of 09:03 GMT/10:03 CET at a distance of 22.5 km from the center of the comet for a nail biting seven-hour trip to touchdown at Agilkia. The burn time to release Philae is only known to within about 30 minutes at this time, says ESA.
Confirmation of a successful landing is expected on Earth at around 16:00 GMT/17:00 CET. Spacecraft signals take about 28 minutes to reach Earth.
The team is actively making final preparations for the momentous event.
“The commands to control the Philae lander are already uploaded,” reported Accomazo.
The Flight dynamics teams specialists are currently making the final plans for the Rosetta spacecraft activities and on-board commands on Tuesday, and they will be uploaded overnight.
“The timing for the Wednesday morning burn (now set for 07:35-08:35CET) is known to only about 30 minutes right now,” said Accomazo.
Between now and separation on Wednesday, there are a series of GO/NOGO decision points to consider for both Orbiter & Lander mission teams. Philae will be activated and tested later today.
“The Lander will be switched on this evening and the control team will start warming it up and getting ready,” said Accomazo.
“If any of the decisions result in a No-Go, then we will have to abort and revise the timeline accordingly for another attempt, making sure that Rosetta is in a safe position to try again,” says Fred Jansen, ESA Rosetta mission manager.
The Agilkia landing site is located on the smaller of the two “lobes” of the bizarre comet and shown in the high-res ESA mosaic herein. The image is about 1 km across.
The touchdown zone is circled and is approximately 500 meters in diameter. It covers about one square kilometer.
The two image mosaic of Philae’s primary landing site was taken by Rosetta’s OSIRIS narrow-angle camera on Sept. 14, 2014, from a distance of 30 kilometers.
Agilkia was previously known as “Site J” and was chosen as the primary landing site from a list of five finalists.
“Site J is named for Agilkia Island, an island on the Nile River in the south of Egypt. A complex of Ancient Egyptian buildings, including the famous Temple of Isis, was moved to Agilkia from the island of Philae when the latter was flooded during the building of the Aswan dams last century,” according to ESA.
Since rendezvousing with the comet on Aug. 6, 2014, after a decade-long chase of over 6.4 billion kilometers (4 billion miles), a top-priority task for the science and engineering team leading Rosetta has been “Finding a landing strip” for the Philae comet lander.
For the past three months, Rosetta’s instruments have been trained on the comet as its top priority to help the sconce and engineering teams find a safe and scientifically interesting landing site.
Following a thorough science, engineering, and hazard assessment of the merits of Agilkia versus the other candidates, ESA’s top management greenlighted the choice in mid-October for deployment of the Philae lander to the “head” of Comet 67P/Churyumov–Gerasimenko for humankind’s first attempt to touchdown on a comet.
“We know a bit more than we did before,” said Matt Taylor, Rosetta Project Scientist, at the briefing.
“It’s a bit warmer than we initially thought; we’re analysing data from several instruments; it’s a more dusty surface material somewhere between hard-packed snow and cigarette ash; there are variations, but we’re seeing this across the planned landing site.”
Agilkia presented the least hazardous terrain of all the landing sites considered during the selection process, says ESA.
Rosetta already made history when it became the first probe from Earth to orbit a comet in August 2014.
As of today, the activity of comet 67P itself is not presenting any obstacles to Philae’s deployment.
“If we see the comet break up, then we have a NOGO,” joked Stephan Ulamec, project manager for Philae from DLR (Deutsche Luft and Raumfahrt), the German Space Agency, at the briefing.
“Seriously, we’ve seen no new activity affecting plans for landing.”
Reams of imagery shows the “surface of the comet is covered in boulders – some larger than houses – as well as steep slopes, deep pits and towering cliffs. In the lower part of this image, the narrowness of the neck region connecting the two lobes is emphasised, with the rugged terrain of the larger lobe in the background.”
After deploying Philae, Rosetta must also reorient itself to establish a communications link with Philae.
During the seven-hour descent, Philae will begin its science operations by snapping images as well as sampling the dust, gas, and plasma environment close to the comet, says ESA. The probes will also take “farewell” photographs of each other. These images will be received back on Earth several hours after the momentous separation event.
Philae’s landing will be entirely automatic. The 100-kg lander is equipped with 10 science instruments.
The three-legged lander will fire two harpoons and use ice screws to anchor itself to the 4-kilometer-wide (2.5-mile) comet’s surface. Philae will collect stereo and panoramic images and also drill 20 to 30 centimeters into the comet to sample its incredibly varied surface.
How will we know that Philae has safely landed?
“We see telemetry signals telling us we’ve touched the surface and that the harpoons have fired,” explained Ulamec.
“It will take ‘several minutes’ to analyse the lander telemetry to confirm landing. One possible problem could be that Philae has landed, but that the harpoons have not anchored; that’s why we need to look carefully at the telemetry.”
Philae is both battery and solar powered. It has enough battery power to survive 2.5 days. Thereafter, it requires solar power to continue operating.
“The first science sequence lasts about 2.5 days (depending on battery life),” noted Ulamec.
“If solar power recharges the batteries, we go into long-term surface science.”
Regardless of the outcome with Philae, the Rosetta orbiter will continue studying the comet’s evolution until late 2015, if all goes well, as it escorts the comet and then arcs away on its outbound voyage past the Sun toward Jupiter.
Why study comets?
Comets are leftover remnants from the formation of the Solar System. Scientists believe they delivered a vast quantity of water to Earth. They may have also seeded Earth with organic molecules—the building blocks of life as we know it.
Any finding of organic molecules will be a major discovery for Rosetta and ESA and inform us about the origin of life on Earth.
On Nov. 11-12, ESA TV will provide live coverage of the key Go/No-Go decisions leading up to the planned landing on Nov. 12.
NASA TV will also broadcast the landing events.
Stay tuned here for continuing developments.
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