Perseverance and the seven minutes of terror – what to expect for today’s Mars landing

FEB. 18, 2021–The long-awaited Mars 2020 mission, carrying the Perseverance rover and Ingenuity helicopter drone, is set to land on Mars today at 12:55 p.m. Pacific (20:55 UTC) in Jezero crater. The landing comes after a months-long cruise since its launch aboard an Atlas V 541 from Cape Canaveral, FL, on July 30 last year.

Perseverance is built on the same architecture and frame as the Curiosity rover, which landed almost a decade ago, with many improvements. It is searching for signs of ancient life and is targeting Jezero Crater, a location NASA believes has “high potential.” Perseverance is also collecting important data about Mars’ geology and climate and carries instruments and technologies that will pave the way for future crewed missions to Mars.

The landing today will be streamed live on NASA TV and several major networks, with coverage beginning at 11:15 a.m. PST, or 2:15 p.m. EST. A timeline of events is included below. Space Scout will also be covering the mission on Twitter under the #CountdownToMars hashtag. A post-landing news conference will also be held at 2:30 p.m. PST.

Mars 2020’s entry, descent, and landing, also known as EDL, will be functionally similar to that of the Curiosity rover which landed almost a decade ago, albeit with some improvements. The mission will impact the Martian atmosphere at a velocity of 5,400 meters per second (12,100 mph), shedding off over 90% of its velocity within 4 minutes of entry. At 4 minutes, the vehicle will deploy its parachute, and separate its heatshield.

However, descent does not end with the parachute. At an altitude of 2.1 kilometers, the parachute and “backshell” are decoupled from the rover and its skycrane. The skycrane is a rocket-powered descent vehicle, made to bring Perseverance down to the surface. At an altitude of 20 meters, the skycrane enters a hover and lowers Perseverance on its winch. After touchdown, Perseverance is decoupled from the skycrane, which then flies away to a safe distance and crashes.

Milestone	PST	Relative to Entry	Velocity
Cruise stage separation	12:38 p.m.	E- 10:00	5,400 m/s
Entry Interface	12:48 p.m.	E+ 00:00	5,400 m/s
Peak heating	12:49 p.m.	E+ 01:20	Unknown
Parachute deployment	12:52 p.m.	E+ 04:00	420 m/s
Heatshield separation	12:52 p.m.	E+ 04:20	160 m/s
Radar lock	12:52 p.m.	E+ 04:50	105 m/s
Terrain-relative navigation	12:53 p.m.	E+ 05:30	89 m/s
Backshell separation	12:53 p.m.	E+ 05:50	89 m/s
Skycrane Powered Descent	12:54 p.m.	E+ 06:00	0.75 m/s
Touchdown	12:55 p.m.	E+ 06:50	0 m/s

If the incredibly complex landing does go according to plan, the Mars Reconnaissance Orbiter (MRO) will be relaying the data within 16 seconds of Perseverance’s landing, as it appears to Earth (All times are adjusted for the light delay to Mars – the landing will be 11 minutes, 21 seconds ahead in time compared to our perception of it). Perseverance itself will also be transmitting some very rudimentary signals – a UHF carrier and X-band tones – directly to Earth. These signals contain very little data and are to confirm what phase of EDL the mission is in and whether the mission is “alive”. If MRO does not immediately relay the data, it will try again 10 minutes and 15 minutes after landing. The MAVEN orbiter will also be flying by, however, it can only relay its data 10 hours after Perseverance lands.

Once the landing sequence is complete, Perseverance will attempt to take its first two images from the front and rear hazard cameras through the clear covers that protect the cameras on descent. These images are expected to be incredibly dusty, but as opposed to Curiosity, will be in color. The “thumbnails” of these images, at a reduced resolution, are expected to be available today. However, depending on where Perseverance lands, MRO may be below the horizon and incapable of immediately relaying the rover’s data.

Later today, quarter-resolution and stereo images from the Hazcams, with the covers open, will be available. By tomorrow morning, high-res images of the wheels and of the descent stage looking down at Perseverance are expected to be available. Over the next few days, Perseverance will take more pictures of the landing site using its navigation and mast cameras, and transmit images from many of the EDL cameras, which will be a first-of-its-kind view of descent.

Perseverance’s first day on Mars – today – will be known as Sol 0, a sol being the 24 hour, 39 minute day on Mars. Within the first 30 Sols, Perseverance will deploy its mast and high-gain antennas, image the rover deck and landing site, update its flight software, perform health checks on its instruments, conduct a 5-meter drive test, test its robotic arms, and more. After the 30-sol period, Perseverance will drive to a flat zone, to test the Ingenuity helicopter.

Ingenuity is a Martian drone and the second part of the Mars 2020 mission, as well as the first flying machine on Mars. The Ingenuity team will, after checkouts, have a month-long period to conduct a series of flight tests with Ingenuity, with Perseverance imaging and recording video of the flights.

As for the rest of the Mars fleet, two of the three Mars missions arriving this month, the Emirati “Hope” probe, and the Chinese Tianwen-1 triple-mission have already arrived successfully at Mars. Hope arrived on February 9 at about 15:42 UTC, and Tianwen-1’s confirmation of orbital insertion was the day after at 12:47 UTC. Both probes endured lengthy “blackout” zones during their insertion burns, in which there was no communication with Earth until well after their burns were complete, much longer than Perseverance’s seven minutes.

The Emirati “Hope” (Arabic: Al-Amal, الأمل) orbiter launched from the Japanese Tanegashima spaceport aboard an H-IIA rocket on July 19, 2020. Hope’s operations are led by the Mohammed bin Rashid Space Center (MBRSC) and the orbiter was developed by the MBRSC alongside multiple American universities, being assembled at the University of Colorado Boulder and with support of Arizona State University and the University of California, Berkeley. Hope’s mission is to study weather cycles on Mars, and events such as dust storms, as well as why Mars is losing so much hydrogen and oxygen into space. 

Tianwen-1 is a Chinese mission launched on July 23, 2020, aboard a Long March 5 rocket from Wenchang spaceport. Tianwen (literal translation: heavenly questions) is a three-part mission. Though it successfully completed orbital insertion a week ago, the lander and rover will only deploy to the surface sometime in May or June. Tianwen’s goal is to find evidence for current and past life, produce Martian surface maps, develop a greater understanding of Martian soil, and study the Martian ionosphere. Notable payloads on the orbiter and rover include a high-resolution camera with a two-meter resolution on the orbiter, and a ground-penetrating radar on the rover, capable of imaging 100 meters below the surface.

Perseverance launched on July 30, 2020, on board an Atlas V 541 from Cape Canaveral, FL. Today’s landing will be the conclusion of a months-long wait, and hopefully, the beginning of a years-long mission. For further reading, view NASA’s Mars 2020 toolkit.

GO Perseverance and Ingenuity, GO NASA, and GO Mars 2020.