CAESAR is a planned proposal for the fifth mission in NASA’s New Frontiers Program. Its goal is to collect material from the surface of Comet 67P and return to Earth with one of the largest samples from space since the Apollo moon missions.
Upon arrival at Comet 67P, CAESAR’s plan is to perform a brief touch-and-go maneuver at a carefully selected location on the surface: Relatively smooth terrain, free of boulders and rugged cliffs, and rich in organic materials and ices. As the spacecraft descends, it would tip its large solar arrays backward, use a long robotic arm to deliver the sampling device to the surface, and then use jets of gas to quickly push material into a container.
After the spacecraft backs away, the arm would place the sample into a containment system on the spacecraft to be preserved in similar conditions to those near the surface of the comet, with temperature and pressure inside the container monitored continuously throughout the rest of the mission.
A few years later, a capsule containing the sample would arrive back at Earth and enter the atmosphere. A specially designed heat shield can protect and help slow the capsule during re-entry but the extreme heat created by this process could damage the sample, so detaching the shield as soon as it is no longer needed is planned to minimize the sample container’s exposure to heat.
Parachutes would also deploy and lower the capsule to its designated landing site at the Utah Test and Training Range, with helicopters standing by to quickly locate and retrieve the sample. Next, a cold storage vehicle nicknamed “the ice cream truck” would transport it to a nearby hangar with a plane waiting to take it to its final destination, the Johnson Space Center’s Curation Facility. The capsule is being designed to keep the sample well below the freezing point of water until it is safely stored in the truck. Once the comet material reaches the curation facility, a detailed process is being developed to carefully remove, preserve, and distribute the sample to be studied by scientists around the world for decades to come.
By targeting Comet 67P, which has already been thoroughly studied by the Rosetta spacecraft, CAESAR can minimize cost and risk. Our extensive knowledge of the comet’s surface is allowing engineers to design hardware well suited for conditions there. Rosetta and its Philae lander have already done all the necessary science at the comet, allowing CAESAR’s emphasis to be on sample collection. The spacecraft need only carry cameras, a sampling device, and a containment system. Also, many of CAESAR’s instruments and hardware have already been used and proven on previous and current missions, which further minimizes cost and risk.
The planned trajectory for CAESAR requires spending its first four and a half years catching up to Comet 67P. On the way it would pass by Earth about a year after launch to gain speed with a gravity assist and calibrate the cameras by imaging the Earth and Moon.
After arriving at the comet, the spacecraft would spend four and a half years imaging the surface in high resolution, documenting how the comet has changed since Rosetta was in orbit, and picking the best sampling site. Several trial runs of the descent to the surface are planned to make sure the sampling device can gently touch the surface safely and with great accuracy. Once all preparations are completed, the spacecraft can perform the touch-and-go maneuver to ultimately collect the sample, and if the first attempt is not successful there is the possibility to try again. After leaving the comet with the sample safely aboard, CAESAR would embark on a four-year journey back home, bringing with it a gift of science for generations to come.
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From the 2018 Lunar Planetary Science Conference.