Only four days now remain before NASA despatches its next robotic explorer to Mars. The long-awaited Perseverance rover—equipped with seven scientific instruments to sniff out the biosignatures of past life, assess the behavior of dust as part of efforts to better understand the Martian weather and test-fly a helicopter on another world for the first time—is scheduled to launch atop a United Launch Alliance (ULA) Atlas V booster during a two-hour “window” which opens at 7:50 a.m. EDT Thursday. Assuming an on-time launch, Perseverance will spend 203 days in space, before executing a hazardous Entry, Descent and Landing (EDL) on 18 February 2021 to alight in the geologically-rich Jezero Crater, just north of the Martian equator. It is expected that Perseverance will contribute substantially to build knowledge for future In-Situ Resource Utilization (ISRU) on the Red Planet and gather a “cache” of soil and rock specimens which may be retrieved and returned to Earth on a future mission.
As outlined in yesterday’s AmericaSpace article, the mission arose eight years ago and was initially named “Mars 2020”. A six-month science definition phase outlined its objectives and specifically zeroed-in on searching for signs of past life, gathering up to 31 soil and rock samples for possible future return to Earth and demonstrating small-scale ISRU technologies for human missions to Mars. Seven instruments for the rover were selected in July 2014 and in March 2018 a helicopter (subsequently named “Ingenuity”) was also added, in what NASA described as a “high-risk, high-reward” test flight.
In the meantime, the spacecraft and instruments were taking shape in factories and clean rooms across the United States, as well as in France, Norway, Spain and Denmark. In August 2016, NASA awarded ULA the contract to launch the rover atop its Atlas V booster. And as the hardware came together, so too did trajectory planners began to narrow the list of possible landing sites. In February 2017, three candidates—the Columbia Hills, once home to burbling mineral springs; Jezero Crater, thought to have harbored a long-since-dried-up lake; and Northeast Syrtis, a volcanically-warmed potential location of ancient springs—were picked for further study. Finally, in November 2018, Jezero was selected as a “unique area” whose exploration would “revolutionize how we think about Mars and its ability to harbor life”.
Located on the western edge of the Isidis Planitia impact basin, just north of the Red Planet’s equator, the 28-mile-wide (45 km) Jezero Crater offers promising sample locations for many different kinds of rock, including clays and carbonates with high potential to preserve biosignatures of past life. However, the site is also littered with small craters and a massive ancient river delta, which posed a challenge to engineers designing Perseverance’s EDL architecture. Like the Curiosity rover which preceded it, Perseverance will employ a combination of a supersonic parachute and rocket-powered SkyCrane to drop it to the surface. Advances gained following that mission and evolving EDL technologies have allowed the landing zone in Jezero to be narrowed to an area 50 percent smaller than that of Curiosity. As a result, more challenging landing sites could be targeted.
Many of these EDL technologies have been subject to exhaustive testing. In the fall of 2017, the Advanced Supersonic Parachute Inflation Research Experiment (ASPIRE) got underway with the launch of a Black Brant IX sounding rocket from Wallops Island, Va. The flight successfully tested a full-scale mockup of the supersonic parachute and deployment mechanism from an altitude of 26 miles (42 km). Another Black Brant IX-lofted ASPIRE test in September 2018 actually broke a world record for the heaviest payload—some 67,000 pounds (37,000 kg)—ever survived by a supersonic parachute. Although this was about 85 percent greater than the load Perseverance will impart on its parachute, the ASPIRE testing campaign closed out as a tremendous success.
Early in 2018, the rover, its cruise stage, aeroshell and the SkyCrane began the lengthy process of assembly and testing in the Spacecraft Assembly Facility High Bay One at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif. Last fall, separation tests of the pyrotechnics between the rover and the SkyCrane were successfully completed.
Beginning last summer, Perseverance itself really began to take physical shape. Its seven-foot-long (2.1-meter) robotic arm—which houses the rover’s Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) and Planetary Instrument for X-ray Lithochemistry (PIXL) sensors—was installed in June, the “bit carousel” of tools for collecting surface samples and the Ingenuity helicopter were added in August and technicians began fueling its 110-watt plutonium battery, known as the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG). Engineering models of its wheels were installed, ahead of a lengthy series of test-drives last December, during which it rolled backward and forward and pirouetted around in its JPL clean room.
The names of the rover and the helicopter itself were bestowed earlier this year. “Perseverance” came about following a nationwide “Name the Rover” essay contest, directed at students from kindergarten through 12th grade, and garnered over 28,000 applications. Last March, seventh-grader Alexander Mather of Lake Braddock Secondary School in Burke, Va., was declared the winner. And in April, Tuscaloosa County High School 11th-grader Vaneeza Rupani of Northport, Ala., saw her proposed name of “ingenuity” chosen for the helicopter. Rupani had initially submitted this proposal for the rover itself.
Delivered from March Air Reserve Base, near Riverside, Calif., to Cape Canaveral Air Force Station, Fla., back in February, aboard an Air Force C-17 Globemaster airlifter, Perseverance had many months of additional work ahead of it on the Space Coast before launch. Having had its engineering wheels removed, its airbrakes and “flight wheels”—machined from flight-grade aluminum and possessing titanium spokes—were installed in March. Throughout April and May, the rover underwent balance and center-of-gravity tests and the whole payload was stacked, ahead of integration into its fairing and installation atop the Atlas V booster earlier this month.
Delayed several times past the 17 July opening of this year’s Mars “launch window”, due to a combination of technical and other issues, Perseverance is currently slated to depart Earth no earlier than 7:50 a.m. EDT on Thursday. The Flight Readiness Review (FRR) was passed with flying colors last week, with the Launch Readiness Review (LRR) anticipated on Monday to declare its preparedness for launch.
Powered uphill on Thursday by the Atlas V’s single RD-180 engine and four solid-fueled boosters, Perseverance will rise from Earth under a combined 2.4 million pounds (1.1 million kg) of thrust. The solids will separate at 110 seconds into flight, after which the Atlas V Common Core Booster (CCB) will itself be jettisoned from the stack at four minutes and 28 seconds. This will set up the proper conditions for two lengthy “burns” of the Centaur upper stage—the first running for nearly seven minutes, the second for eight minutes—before the payload is set free at T+57 minutes to begin its voyage to Mars.