If all goes to plan, this week we should be getting our first close-up look at a brand new world. On Wednesday 6 August, the European Space Agency's Rosetta spacecraft will rendezvous with the comet it has been chasing for the past 10 years. Mapping and landing on comet 67P/Churyumov-Gerasimenko will be a challenge unlike anything space explorers have faced before."When you go to Mars nowadays, you know everything," says Rosetta flight director Andrea Accomazzo. Not so for Rosetta's target. "We don't know the mass, we don't know the gravity field, we don't know how to fly around this object."Previous spacecraft have flown by comets at high speed. Rosetta, on receiving ESA's commands, sent today, will slow to just 1 metre per second relative to its destination.Because the comet's gravity is so weak, Rosetta will initially manoeuvre around it in a series of controlled triangles. These will start at a distance of 100 kilometres and move closer in over the next few weeks as ESA learns more about the comet's structure. Eventually it will enter a proper orbit determined only by gravity, getting as close as 10 kilometres.Mapping the duckPictures released last month have already revealed the comet is made of two pieces fused together in a shape likened to a rubber duck. That means its gravitational pull tugs in strange and unpredictable directions, so creating a detailed 3D model of the comet is a top navigational priority. "We are acquiring hourly images so we can see the body, reconstruct its shape and characterise features of its surface," says Accomazzo.Missions to asteroids, like NASA's NEAR Shoemaker, have orbited similarly lumpy rocks, but a comet offers new challenges. Gases frozen beneath Churyumov-Gerasimenko's surface could escape explosively as the comet nears the sun and warms up. As they spurt out they will push against Rosetta's solar panels, possibly as strongly as the comet's gravity, but in the opposite direction.Rosetta is in for a bumpy ride, and there will be no time for ESA researchers to catch their breath. Philae, a smaller probe that has ridden along with Rosetta, must touch down on Churyumov-Gerasimenko's surface by 11 November: any delays will make landing much trickier as the comet becomes increasingly active on its approach to the sun.Little time"We have to do this at warp speed. We have very little time between the discovery of a new world and landing," says Holger Sierks, lead researcher on Rosetta's main camera OSIRIS, which will map the comet's surface.Cartographers know the difficulties involved in wrapping a flat map around a globe, but they can at least lay down lines of latitude and longitude with ease when mapping our planet. "It is more difficult to mosaic a highly irregular body like our rubber ducky," says Sierks. "The whole coordinate system on this body is tricky."ESA will announce a shortlist of landing sites in September. Data from all of Rosetta's scientific instruments and measurements of how the comet affects the probe's trajectory will influence the eventual choice.Dark and dustyAccording to measurements released last week, the comet's average surface temperature is -70 °C, around 20-30 °C warmer than predicted. That makes it likely that the surface is dark and dusty rather than coated in clean ice. Understanding how the surface temperature changes as the comet nears the sun will be a factor in where to land, as certain sites may become unstable.One spot that might already be off limits is the "neck" of the duck. Despite being of great scientific interest, it may prove too difficult to touch down on, as gravity may not be acting at a right angle to the surface. "It would be like landing on a slope," says Accomazzo.For now, we can look forward to the first high-resolution images of Churyumov-Gerasimenko, which should be around 100 times better than those already released and will take an hour for the probe to transmit early on Wednesday morning. "It's the end of a 10-year trip in the solar system and the start of the exploration of a new world," says Accomazzo.
European Spacecraft Pulls Alongside CometBy KENNETH CHANGAUG. 6, 2014 After 10 years and a journey of four billion miles, the European Space Agency’s Rosetta spacecraft arrived at its destination on Wednesday for the first extended, close examination of a comet.A six-minute thruster firing at 5 a.m. Eastern time, the last in a series of 10 over the past few months, slowed Rosetta to the pace of a person walking, about two miles per hour relative to the speed of its target, Comet 67P/Churyumov-Gerasimenko.“It is like driving a car or a bus on a motorway for 10 years,” said Andrea Accomazzo, the flight director, at a post-rendezvous news conference. “Now we’ve entered downtown. We’re downtown and we have to start orienting ourselves. We don’t know the town yet, so we have to discover it first.”Over the coming months, Rosetta and its comet, called C-G for short, will plunge together toward the sun.In November, a small 220-pound lander is to leave the spacecraft, set down on the comet and harpoon itself to the surface, the first time a spacecraft has gently landed on a comet.At this point, the comet and its shadowing spacecraft are more than 330 million miles from the sun (more than three times as far out as Earth), traveling at 35,000 miles per hour. With the final firing of the thruster, Rosetta was a mere 60 miles from the comet’s surface.“This morning, we hit a milestone, an important milestone of this mission,” said Laurence O’Rourke, a member of its science team.“But this mission isn’t just about arriving at a comet,” he went on. “It’s about studying the comet. It’s about placing a lander on a comet, but again the mission does not end there. The science continues. We’re trying to follow this comet all around its orbit.”Rosetta is still not close enough to be captured by the comet’s gravity, but instead will be flying a triangular path in front of the comet as it maps the surface. It will eventually move within 6.2 miles of the surface and enter orbit around the comet.Comets, made of ice, dust and rock, are frozen leftovers from the formation of the solar system. Rosetta is named after the Rosetta Stone, the engraved block that was crucial in deciphering Egyptian hieroglyphics, and scientists hope the spacecraft’s observations will offer important clues to how the solar system came together 4.5 billion years ago. (Rosetta’s lander, Philae, is named for an island in the Nile River.)Photographs have revealed a surprisingly irregular shape for the two-and-a-half-mile-wide comet, possibly an amalgamation of two icy bodies or a result of uneven weathering during previous trips to the inner solar system. From a distance, the blurry blob looked something like a rubber duck; as the details came into focus, it began to bear a closer resemblance to a knob of ginger flying through space.At the news conference, Holger Sierks, the principal investigator for Rosetta’s high-resolution camera, revealed the latest images, pointing to cliffs, deep shadows and also flat areas with boulders sitting on the surface. “We’ll learn in the coming months what this is telling us,” he said.The spacecraft had earlier measured the flow of water vapor streaming off the comet at a rate of about two cups a second, which would fill an Olympic-size swimming pool in about 100 days. As the comet accelerates toward the sun, its surface will warm, and the trickle will grow to a torrent a hundred or a thousand times that size, contributing to the long tail that is characteristic of comets.Measurements in July put the average surface temperature at minus 94 degrees Fahrenheit, or minus 70 Celsius. That was warm enough to indicate that the surface was not exclusively ice and that some parts were dusty and darker, absorbing more heat from the sun.An unsolved mystery of Earth is where the water in the oceans came from; some suggest it came from comets. The water in comets from the distant Oort Cloud, far beyond Pluto, does not match the water on Earth, but the water in nearer comets may.C-G is one of the nearer comets: Its orbit extends not far beyond Jupiter. Scientists should now be able to get a better idea of its composition by measuring temperatures at its surface and a few inches below, and in the gases streaming off the comet, along with the weight of water molecules streaming off it.Much of the work in the next three months is to find a safe place for Philae to land. Once released from Rosetta, the lander will be pulled down by the comet’s gravity and will strike its surface at a couple of miles per hour, like someone walking into a wall. “It’s hurting but it doesn’t kill you,” said Stephan Ulamec, head of the consortium that built the lander.The harpoons and a thruster will help keep it from bouncing off, although Dr. Ulamec said recent photographs suggested a dusty surface more like cigarette ash or newly fallen snow than hard ice. “But actually we do not know it yet,” he said. “We will only find out when we land there.”Designed to operate through 2015, Rosetta and Philae will make observations as the comet makes its nearest approach to the sun a little more than a year from now, at 115 million miles, still outside the orbit of Earth. The comet will remain too dim to be seen by the naked eye.Other missions to comets have made brief flybys, beginning with the International Sun-Earth Explorer-3 in September 1985. NASA’s Deep Impact slammed into a comet in 2005, and another mission, Stardust, has collected particles of dust and returned them to Earth for study.(ISEE-3 is back in the news, because the spacecraft, still largely working, will zip past Earth again on Sunday.)The $1.7 billion Rosetta mission will provide a much longer, much closer look at one comet. Instead of taking a brief snapshot, the spacecraft will observe C-G going from a quiescent ball of ice and rock to an active comet spewing out dust and gas and then make before-and-after comparisons.Launched in March 2004, Rosetta — a boxy structure roughly nine by seven feet, powered by two 47-foot-long solar panels — followed a circuitous route through the solar system, using flybys of the Earth and Mars to fling itself into the same orbital path as Comet C-G. In January, it emerged from a hibernation of two and a half years and began its final approach.
Europe's Rosetta mission, which aims to put a robot on Comet 67P/Churyumov-Gerasimenko, has identified five potential locations for the touchdown.The choice of sites was driven largely by operational considerations - they are places engineers believe a lander can get down with the least risk.No-one has attempted to land on a 10-billion-tonne comet before.The Rosetta probe will despatch its Philae contact robot to 67P's icy surface on 11 November.The European Space Agency says it will be a one-shot opportunity.Rosetta and the comet are currently about 400 million km from Earth, making real-time radio control impossible.Instead, the process will have to be fully automated with commands uploaded several days in advance.The five sites on the "longlist" were selected at the end of a special meeting convened in Toulouse, France, this past weekend.Esa project managers were joined by attendees from the space agencies of France (Cnes) and Germany (DLR), which play key roles in the Philae effort.Instrument principal investigators on the washing machine-sized robot were also there to argue their preferences, as were the engineers, who could explain the technical possibilities.If one considers the comet to look like a rubber duck, then three of the chosen potentials (B, I and J) are on the head. Two are on the body (A and C). The dramatic neck region has been ruled out.The letter designation stems from an even longer list of 10 that was used to kick-off the whole selection process. The letter ordering carries no weight.A landing site needs to be relatively flat and free from boulders and fissures.One key requirement has been the need to find places on the comet that experience something of a day/night cycle.This will give not only a better appreciation of the changing behaviour of 67P under all conditions, but will provide the lander with some important protection - from too much sun, which could lead to overheating, or too little light, which would make it difficult to charge the batteries.The engineers have also emphasised the need to find locations where Rosetta can deliver Philae at the right altitude and velocity, and maintain a communications link throughout the descent, which is likely to take several hours.The longlist will be reduced to a leading candidate and perhaps a couple of back-ups in mid-September.A final go/no-go decision on a target landing site is expected by mid-October.By then, Rosetta's cameras and other instruments will have returned detailed data on the number one choice.Comet 67P has very little gravitational attraction - several hundred thousand times weaker than what Philae would experience at the Earth's surface. For this reason, it will touch down at no more than a walking pace - about 1m/s. It will use harpoons and ice screws to try to hang on to the comet and avoid bouncing back into space.
No easy parking spot for first-ever comet landing16:25 09 September 2014 by Stuart ClarkLanding on a comet will be even harder than we thought. The strange shape of comet 67P/Churyumov-Gerasimenko does not present as many safe landing sites for the European Space Agency's Rosetta spacecraft as mission planners had hoped."Its shape is exciting scientifically but it [creates] a lot of challenges," says project scientist Matt Taylor at the European Space Research and Technology Centre in Noordwijk, the Netherlands. He calls the comet "the duck" because from some angles it resembles a rubber one.The probe arrived at 67P on 6 August after a 10-year journeyMovie Camera. The plan is to release a probe called Philae to land on the comet's surface on 11 November. ESA announced five candidate touchdown sites on 25 August, but on 8 September at the European Planetary Sciences Congress in Cascais, Portugal, the team admitted that none of the sites looked very safe."All landing sites are worse than expected because of the shape of the body," said the lander's lead scientist, Hermann Böhnhardt of the Max Planck Institute for Solar System Research in Göttingen, Germany. Worse means smaller. Philae is designed to land within an ellipse 1 kilometre in length. Of the five shortlisted sites, only site B (pictured below), at the "head" of the duck, meets that requirement. There are some larger, smoother sites on the base of the duck's "body" but they are too poorly lit to let the lander recharge its batteries during its four-month mission.New images from Rosetta's high-res camera reveal what appear to be layered cliffs across the comet. These are good for determining the comet's history, but could damage Philae if it hits them.Once Philae leaves Rosetta, there will be no chance to alter its trajectory. It will take 5 to 8 hours to drift to the surface under the comet's weak gravity. Should it hit rough ground and tumble on to its side, some science may still be possible, but settling upside-down would almost certainly spell doom for the lander mission.Meanwhile, Rosetta has captured its first grains ejected by the comet and shown that such emissions vary throughout its 12.4-hour day. 67P ejects most particles in the afternoon from the duck's "neck". Examining this site could help show if the comet began life as one body or two.
Rosetta: landing site chosen for first comet mission13:04 15 September 2014 by Jacob AronWhen it comes to comets, J marks the spot. The European Space Agency has announced the landing site for its Rosetta mission to comet 67P/Churyumov-Gerasimenko, following a meeting this weekend to whittle down a shortlist of five possibilities.The J landing spot, on the "head" of the comet, was chosen for having the smoothest surface, but that doesn't mean Rosetta's lander probe, Philae, will touch down without incident. "There are flat areas but there is also rough terrain, there are some cliffs and some boulders," says Stephan Ulamec, who is in charge of Philae. "It is not an easy task."ESA will hold a public competition to come up with a better name for the landing site.Philae will be released in mid-November – the exact date will be confirmed later this month – and take seven hours to reach the comet's surface. Rosetta will have to constantly manoeuvreMovie Camera as it orbits 67P to keep in touch with Philae and let ESA monitor the landing process.Easier landingIf ESA discovers that J is unsuitable between now and November, they have selected a backup site, C. Landing on this spot would give Philae a view of the comet's "neck", which is of high scientific interest, but J won out as the easier place to touch down. Switching to the backup could delay landing by four weeks, as ESA will have to redo its plans for the descent and scientific analysis. "We might be able to skip certain steps, but there is a potential delay," says Rosetta mission manager Fred Jansen. When Philae lands, its first task will be snapping a 360-degree panorama of the surface, along with measurements of the gas pressure and dust distribution at the landing site. Later, it will drill beneath the surface and analyse pristine comet material. It is hoped that Philae will also see jets of gas and dust emerging from nearby pits as the comet heats up as it travels towards the sun.The comet's duck-like shape makes the job of landing far more complex, says Jansen. Before arriving at 67P, ESA had expected a roughly spherical comet and predicted a 70 to 75 per cent chance of a successful landing. Now it hasn't dared to calculate the odds, as the show must go on regardless. "Lander delivery has to happen for the mission to continue," says Jansen.
7 Gadgets Rosetta Is Sending To the Surface of the CometLast week, the European Space Agency announced a final date—November 11—for when it will release its Rosetta lander, a tiny pod called Philae, down to the surface of the comet. Like a cosmic hobo carrying a stick and bindle, it will travel laden with only the essentials. Thanks to Universe Today, ESA, and NASA, we know what it's bringing. The tools and instruments that will accompany Philae down to the surface of comet 67P/Churyumov–Gerasimenko are crucial. It's our first chance to truly analyze a comet, and these mechanisms will be responsible for it. Universe Today's Tim Reyes points out that Philae weighs only 220 pounds, so all of the instruments it's bringing are absolutely essential, and have been whittled down to be as light and tiny as possible. Photovoltaic PanelsAgain, Philae is light—and it doesn't have a whole lot of battery power to work with. So it will bring with it a series of photovoltaic panels, 21 square feet in all, to power all of its busy days spent digging, listening, and analyzing the comet.Sensors to Listen to the CometAs part of a package that includes sensors to measure things like permittivity, Philae will also send acoustic waves across the comet using a transmitter! Then, with receivers embedded in its legs, it will measure how they bounce off and through the comet. According to Reyes, they'll also record audio of the "creaks" and "groans" on the surface. A Transmitter To Send Radio Through the Comet's CoreESA's team is interested in what's inside the comet, so they'll use a simple method to get some basic measurements: Radio. While Rosetta orbits around the side of the comet opposite of the lander, it will put out radio waves which Philae will receive and return. Essentially, they're performing tomography—imaging the interior of the comet by sending waves through it and listening to how they distort and move.A Hammering Arm to Bury Sensors In the SurfaceHere's a fascinating one: A mechanical arm will "hammer" up to a foot into the comet's surface with an accelerometer and a thermometer at its tip—measuring not only the thermal makeup, but how deep the hammer can punch before it's stopped. Other sensors will measure the temperature of the comet as it gets closer to the blazing hot sun. A DrillRosetta and Philae are on a mission to analyze—or "taste," as the ESA says, the dust and ice on the comet. So Philae will use a drill to collect and then transport surface samples to a series of ovens where they'll be studied by the other devices on the lander. Since the little lander doesn't have much power to work with, the ESA says the drill consumes only a hundredth of the power your average drill does. Here's where it's located, shown on a replica of Philae:CamerasA system called CIVA-P (which weighs less than 100 grams!) will shoot color and infrared images of the landing site, while another imaging system called ROLIS will shoot images of the process of landing, along with close-ups of the comet's surface.A Spectrometer To Measure Chemical MakeupThis device can measure the chemical makeup of samples on comet 67P/Churyumov–Gerasimenko's surface—how much hydrogen or helium exists up (down?) there, for example—by exposing samples to radiation. That radiation creates energy by interacting with the samples, which the spectrometer can measure.
A European spacecraft's comet companion is starting to wake up as it gets closer and closer to the sun.The European Space Agency's Rosetta probe, which arrived in orbit around Comet 67P/Churyumov-Gerasimenko in August after a 10-year deep-space chase, has photographed jets of gas and dust erupting from the icy wanderer's surface."The main talking point of this image is the spectacular region of activity at the neck of 67P/C-G," European Space Agency (ESA) officials wrote in a description of the photo, a four-image montage taken on Sept. 26 when Rosetta was 16 miles (26 kilometers) from the comet. "What we’re seeing is the product of ices sublimating and gases escaping from inside the comet, carrying streams of dust out into space," they added. "As the comet gets progressively closer to the sun along its orbit, the surface will become warmer, and the level of activity will increase, producing a vast coma around the nucleus, along with a tail."The $1.7 billion (1.3 billion euros) Rosetta mission launched in March 2004 and took a circuitous path through space, finally catching up to the 2.5-mile-wide (4 km) Comet 67P on Aug. 6 of this year. On that date, Rosetta became the first probe ever to orbit a comet.The Rosetta team aims to make some more history soon. On Nov. 12, the probe will deploy a lander called Philae, which will spiral slowly down toward 67P and, if all goes according to plan, become the first robot to make a soft touchdown on a comet. Philae will snap photos and analyze samples of the comet.Rosetta should continue studying 67P through at least December 2015, observing how the icy body changes as it approaches the sun. The mission's data should reveal a great deal about comet composition and, by extension, the early days of the solar system, mission team members say. (Comets are "time capsules" of material left over from the solar system's formation.)
ESA Confirms Rosetta's Landing Site On Rubber Ducky Comet Now comes the hard part: actually landing.By Loren GrushPosted 10.15.2014 at 2:03 pm After more than 10 years of traveling through space, the Rosetta spacecraft -- the first space vehicle to travel to a comet -- is finally taking a load off. Well, part of it is, anyway.This morning, the European Space Agency confirmed the landing site for Rosetta’s lander, Philae, on comet 67P/Churyumov-Gerasimenko. Out of five potential areas for touchdown, a region known as Site J was picked for the historic landing, which is currently scheduled for November 12. Site J is located on the smaller of the comet’s “lobes” (or the “head” of the rubber ducky-shaped comet).The landing will mark the first time a spacecraft has touched down on a comet. But the mission won’t exactly be a cakewalk. There’s still a lot more to be done before the landing can happen, and comet 67P’s weird shape means there’s a significant chance the 220-pound lander will more crash than land.On November 11, the day before the expected touchdown, the flight dynamics team will have to make a series of “Go/No-Go” decisions in order to determine that Rosetta is where it needs to be to deliver Philae safely. Since Rosetta arrived at the comet on August 6, it has been moving closer to the comet body every day. Right now, it’s about 10 kilometers away from 67P, which is only 4 kilometers wide itself. But on landing day, the spacecraft will need to be 22.5 kilometers away from the comet’s center.Two hours before Philae is released, Rosetta will perform a short maneuver to ensure the lander is on the right trajectory to land (and not crash). As of now, Philae’s separation is scheduled for 8:35 am GMT, or 3:35 in the morning for those on the East coast. The landing will occur about seven hours after that, but because of the travel signal time between Rosetta and Earth, we won’t know if it made it down safely until 28 minutes later.During its descent to 67P, Philae will take pictures and even perform a few experiments, testing the dust and plasma environment surrounding the comet. Once it makes it to its new home, Philae has about 64 hours of primary battery life to conduct its first sequence of science experiments.After that, lengthier experiments kind of all depend on how much longer the batteries can last. Philae has solar panels for generating energy, but the team expects that dust will eventually settle on them, complicating the process. Man, if only 67P had an outlet...Finally, in March 2015, the comet will have moved along its orbit, bringing it much closer to the sun. By that point, Philae will be so hot that it can’t continue with its work, and the whole operation will come to an end. But though we will have lost a lander, hopefully we will have gained a significant understanding about the evolution of comets -- and the origins of our Solar System.
