Keep the shuttle flying: Fwd: All is ready for historic comet landing

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From: "Gary Johnson" <gjohnson144@comcast.net>
Date: November 11, 2014 11:21:34 AM CST
To: "Gary Johnson" <gjohnson144@comcast.net>
Subject: FW: All is ready for historic comet landing

All is ready for historic comet landing
November 10, 2014 by Stephen Clark
Philae's target — named Agilkia — is seen above the boulder-filled depression near the top of this image of comet 67P/Churyumov-Gerasimenko. Image credit: ESA/Rosetta/NAVCAM
DARMSTADT, Germany — This week marks the pinnacle of the professional careers of many scientists, when the European Space Agency plans to put down a three-legged robotic lander on a comet, a risky first-of-a-kind endeavor that could rewrite textbooks on the history of the solar system.
The landing of Philae — a spacecraft about the size of a kitchen oven — is scheduled for Wednesday after a perilous seven-hour descent from Europe's Rosetta orbiter, which arrived at comet 67P/Churyumov-Gerasimenko in August.
"I think this is the key week of our professional careers," said Andrea Accomazzo, Rosetta's flight director at the European Space Operations Center here. "I don't think we will land on a comet any other time (in our careers)."
The lander has been feeding off of Rosetta's power supplies since the missions launched together in March 2004, but Philae will cut the umbilical and fly free of its mothership Wednesday.
Release is scheduled for 0903 GMT (4:03 a.m. EST) Wednesday in "Earth time." The real event will occur more than 28 minutes earlier, but it takes nearly a half-hour for radio signals to cover the distance between Earth and Rosetta.
Confirmation of landing on the comet is expected around 1600 GMT (11 a.m. EST), but officials say the time could vary by a few minutes due to uncertainties in Philae's trajectory.
The landing is the culmination of three months of feverish surveys, scientific and engineering reviews and decisions to settle on an acceptable touchdown zone for Philae.
The selected site is named Agilkia after an island in the Nile River in Egypt, and although the region is deemed the safest on the comet for landing, it contains some boulders and slopes that could spell trouble for Philae.
The Agilkia site sits on the smaller of the comet's two lobes — the "head" of the rubber duck descriptor often used to describe the comet's shape. Comet 67P/Churyumov-Gerasimenko is about the size of a small city.
"We've put all the effort we could put into this activity," Accomazzo said. "There's still a lot in front of us. There are many things that depend on what we are going to do in the net couple of days, and there are a couple of things that do not depend at all on what we do. For example, where we touch down. We cannot select a single spot where we touch down. We need to be a bit lucky."
Scientists have plans for Philae and Rosetta to work in tandem over the next few months studying the comet, sniffing and tasting its chemical components, and looking for signs of water and organics that could have been essential to the emergence of life on Earth.
The lander has a 64-hour battery lifetime, but it could run on solar power until spring, when it is expected to overheat as the comet nears the sun.
Rosetta will continue flying around the comet until at least the end of 2015, collecting its own independent measurements.
"This week marks an epoch in the mission," said Matt Taylor, ESA's project scientist for the Rosetta mission. "Once this week has passed we start the full science phase. It's all about science then. Up to now, we have been doing science on the side enabling landing site decisions and characterization of the comet."
The lander was set to be activated late Monday, according to Stephan Ulamec, who leads the Philae team at DLR, the German Aerospace Center.
"We will start with warming it up, and then in the following hours we will prepare it for separation and descent," Ulamec said. "For the moment everything is go. The commands are uploaded, and the lander is ready to be ejected on Wednesday in the early morning and land later in the afternoon (European time)."
Sylvain Lodiot, Rosetta's spacecraft operations manager, said ground controllers here would begin 24-hour shifts Tuesday and stay on console around the clock through the weekend.
"The two teams doing this shiftwork in flight dynamics have done massive work in the last few days, and I think we're ready," Lodiot said.

© 2014 Spaceflight Now Inc.

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November 10th, 2014
Bullseye! Rosetta Orbiter Locks on Audacious Agilkia Comet Landing Site
By Ken Kremer
The Agilkia landing site is seen in this image of Comet 67P/Churyumov–Gerasimenko, taken with Rosetta's navigation camera on 6 November, just days before its lander Philae makes its historic descent to the surface. Credits: ESA/Rosetta/NAVCAM, CC BY-SA IGO 3.0
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 bulls eye view of the utterly alien 'Agilkia' landing site.
The orbiters 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 12 November for the daring attempt at a safe touchdown on a comet for the first time in human history.
Philae must endure '7 hours of terror' between departure from Rosetta and touch down 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.
Rosetta & Philae at comet 67P. Credit: ESA–C. Carreau/ATG medialab
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 14 September 2014 from a distance of 30 kilometers.
Philae's primary landing site from 30 km. Close-up of the region containing Philae's primary landing site J, which is located on the 'head' of Comet 67P/Churyumov–Gerasimenko. The mosaic comprises two images taken by Rosetta's OSIRIS narrow-angle camera on 14 September 2014 from a distance of about 30 km. The image scale is 0.5 m/pixel. The circle is centred on the landing site and is approximately 500 m in diameter. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
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 August 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 vs. 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 humankinds 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.
A timeline of the science operations that Rosetta's lander Philae will perform during the first 2.5 days on the surface of Comet 67P/Churyumov–Gerasimenko. Credit: 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 (2.5 mile) wide 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 two and a half days. Thereafter it requires solar power to contine 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 outcomne 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 towards Jupiter.
Jets are blasting from the active neck of comet 67P/Churyumov-Gerasimenko in this four-image photo mosaic comprising images taken on 26 September 2014 by the European Space Agency's Rosetta spacecraft at a distance of 26.3 kilometers (16 miles) from the center of the comet. See the montage ot four individual navcam images below. Credit: ESA/Rosetta/NAVCAM/Marco Di Lorenzo/Ken Kremer – kenkremer.com
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 11–12 November, ESA TV will provide live coverage of the key Go/No-Go decisions leading up to the planned landing on 12 November.
NASA TV will also broadcast the landing events.
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Risky Comet Landing by European Probe Will Be '7 Hours of Terror'
by Elizabeth Howell, SPACE.com Contributor | November 10, 2014 02:00pm ET

Landing a probe on a comet whizzing through deep space isn't easy, but this week, the European Space Agency (ESA) will attempt to do just that. If successful, it will be the first time a probe has landed on the surface of a comet.Officials working with ESA's Rosetta mission are planning to land the robotic Philae probe on Comet 67P/Churyumov-Gerasimenko's surface this Wednesday (Nov. 12). You can track Philae's historic progress in live webcasts from ESA and NASA starting Tuesday (Nov. 11) and throughout the day Wednesday. Officials on Earth should know if the landing went well by 11:02 a.m. EST (1602 GMT) on Nov. 12.
The landing is a risky operation.
Detailed mapping of Comet 67P/C-G only began in August, when Rosetta arrived carrying Philae. The comet's surface is strewn with boulders and cracks, and Philae's landing system has no way to maneuver at the last minute. [See amazing images from the Rosetta mission]
It will take about 7 hours for scientists on Earth to find out if Philae's trip to the surface was successful. A NASA video has even dubbed that block of time "7 hours of terror," an homage to the NASA Curiosity rover's "7 minutes of terror" video that described the Mars rover's landing sequence.
"This comet is very, very rough," Andreas Accomazzo, Rosetta operations manager at the European Space Agency, said in a Google+ Hangout Friday (Nov. 7). "But this is what we have, and this is what we are trying to do. We have to be a bit lucky as well."
The two-part Rosetta spacecraft is designed to orbit and land on the Comet 67P/Churyumov-Gerasimenko in November 2014. See how the Rosetta spacecraft works in this Space.com infographic.
Credit: by Karl Tate, Infographics Artist
View full size image
First comet landing
If Philae's landing is successful, it will crown Rosetta's decade-long journey in space. The mission is doing the first orbit of a comet right now.Rosetta has already become the first spacecraft to orbit a comet, and if Philae safely touches down on Comet 67P/C-G, the lander will be the first to make a soft landing on a comet.
A comet is a tough environment. The gravity is so low that Philae will need to deploy a harpoon into the surface in order to stay put on Comet 67P/C-G. During landing, the spacecraft will face a dusty environment — not to mention, rocks on the surface. Success will also largely depend on how well the probe's hardware and software perform during those final few hours on the way down.
Rosetta planners will spend today (Nov. 10) and Tuesday looking at the landing orbit and preparing the parent spacecraft to release Philae. One of the busiest times will be late Tuesday night, when controllers have only 4 hours to send commands to Philae and make sure it's ready to go. [See more news about the Rosetta mission]
"We have 4 hours to put them together, check to verify they are consistent, uplink to the spacecraft ... and double-check they are OK to the spacecraft," Accomazzo said. "It's a pretty dense set of activities we have to do."
The plan then calls for Rosetta to release Philae Wednesday at 3:35 a.m. EST (0835 GMT). (ESA officials on the ground will find out if the release was successful 28 minutes and 20 seconds later, once the signal reaches Earth.)
The spacecraft is too far away for controllers to do anything but hold their collective breath as the probe makes its descent. ESA mission controllers should acquire a signal from Philae during its descent at about 5:53 a.m. EST (1053 GMT). Once that signal is established, Rosetta can start beaming back science information gathered by Philae on its way down to the comet's surface.
And by about 11 a.m. EST (1600 GMT), scientists should know if Philae reached the surface.
Rosetta will also need to make several maneuvers to stay in touch with Philae during its descent, landing and post-landing activities. ESA added that both Rosetta and Philae appear to be in good shape to date, so they are planning for the best.
Not all science would die with Philae
Even if Philae doesn't successfully land, ESA anticipates that only 20 percent of the scientific findings expected to be gathered from the Rosetta mission would be lost. The remaining science would come from the orbital mission, which is projected to remain active until at least December 2015 — five months past Comet 67P/C-G's closest approach to the sun.
Philae's potential landing would make it the seventh location in which spacecraft have touched down outside Earth. The other bodies visited include Venus, the moon, Mars, Saturn's moon Titan, and asteroids 433 Eros and Itokawa.
"It's a very, very risky business, but it's a business in which we have invested a lot of know-how — a lot of technical know-how, a lot of scientific know-how and a lot of cooperation," Jocelyne Landeau-Constantin, head of European Space Operations Centre communications, said in the same webcast.
"Sometimes, we wake up and wonder if this dream is going to be true," she added. "Sometimes, we know it can go wrong. But we are ready for every option, and are still very confident we can make it."

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