Deceleration of Mars Science Laboratory in Martian Atmosphere. Artist's Concept depicts the interaction of NASA's Mars Science Laboratory spacecraft with the upper atmosphere of Mars during the entry, descent and landing (EDL) of the Curiosity rover onto the Martian surface. EDL begins when the spacecraft reaches the top of Martian atmosphere, about 81 miles (131 kilometers) above the surface of the Gale crater landing area, and ends with the rover safe and sound on the surface of Mars some 7 minutes later. During EDL, the spacecraft decelerates from a velocity of about 13,200 miles per hour (5,900 meters per second) at the top of the atmosphere, to stationary on the surface. Credit: NASA/JPL-Caltech
In the coming decades, a number of missions are planned for Mars, which include proposals to send astronauts there for the first time. This presents numerous logistical and technical challenges, ranging from the sheer distance to the need for increased protection against radiation. At the same time, there is also the difficulty of landing on the Red Planet, or what is referred to as the “Mars Curse“.
To complicate matters more, the size and mass of future missions (especially crewed spacecraft) will be beyond the capacity of current entry, descent, and landing (EDL) technology. To address this, a team of aerospace scientists released a study that shows how a trade-off between lower-altitude braking thrust and flight-path angle could allow for heavy missions to safely land on Mars.
When Curiosity executed a perfect six-wheel landing on Mars on the morning of August 6 to the excitement of millions worldwide — not to mention quite a few engineers and scientists at JPL — it immediately began relaying images back to Earth. Although the initial views were low-resolution and taken through dusty lens covers, features of the local landscape around the rover could be discerned… distant hills, a pebbly surface, the rise of Gale Crater’s central peak — and a curious dark blur on the horizon that wasn’t visible in later images.
What could it have been? Another bit of lens dust? An image artifact? A piece of ancient Martian architecture that NASA demanded be erased from the image? As it turns out, it was most likely something even cooler (or at least real): the result of Curiosity’s descent stage crash-landing into the Martian surface.
Seen in an image from NASA’s Mars Reconnaissance Orbiter’s HiRISE camera, the remnants of Curiosity’s descent to Mars are scattered around the landing site. The heat shield, parachute, back shell — and undeniably the star player of Curiosity’s EDL sequence, the descent stage and sky crane — all landed in relatively close proximity to where the rover touched down. As it turned out, Curiosity’s’s rear Hazcam happened to be aimed right where the sky crane landed after it severed Curiosity’s bridles and rocketed safely away — just as it had been shown in the landing animation.
Seen in the first images captured by Curiosity’s rear Hazcams just minutes after touchdown — but not in higher-resolution images acquired later — the dark blur is now thought to be a plume of dust and soil kicked up by the sky crane’s impact.
“We know that the cloud was real because we saw it in both the left and right rear Hazcams, so it wasn’t just a smudge on the lens cover or anything like that… and then 45 minutes later it was gone,” said Steven Sell, Deputy Operations for Entry, Descent and Landing at JPL, during an interview with Universe Today on Friday.
“When we were putting together the sequence of images of what would happen after touchdown, we specifically put in the Hazcam shots as soon as we could on the off chance that we would see something,” Sell said. “It was just one of those things where we had some choices we could make, and we said if we put these really close to landing maybe we’ll actually see part of the descent stage.”
Although capturing the sky crane or other part of the descent stage on camera was an intriguing idea, it wasn’t any particular goal of the mission.
“We know that the cloud was real because we saw it in both the left and right rear Hazcams, so it wasn’t just a smudge on the lens cover or anything like that.”
– Steven Sell, Deputy Operations for Entry, Descent and Landing at JPL in Pasadena, CA
“We literally weren’t even thinking about it,” Sell said. “It’s a total bonus that we were able to capture that.”
Unfortunately, the plume only appears in the initial Hazcam shots, which were taken through lens covers coated with dust from landing. It wasn’t until nearly an hour later that the covers were removed and clearer images were captured, and by then the plume was gone. Plus the Hazcams themselves are low-resolution by design — they’re more for navigation than landscape photography.
“Those cameras are not intended for doing that kind of science, or even any science at all,” said Sell. “They’re strictly engineering cameras.”
It’s been said that the best camera is the one you have with you, and in this case Curiosity’s best camera happened to be aimed in the right place at the right time. Plus the sky crane just so happened to land in view of the cameras that got turned on first, which wasn’t a guarantee.
“The descent stage had two possible directions to go: it could have gone forward or backward,” Sell explained. “The way it decides which way to go is whichever direction would take it more north. We knew that the science target is toward the south — the scientists want to study the mountain — and so we didn’t want to throw the descent stage toward the mountain.
“The good news is that the forward Hazcams were at a lower temperature upon landing, we knew they were going to be colder,” Sell said. “The cameras have to reach a certain temperature before they can take a picture, so we knew the rear Hazcams were going to get the picture first, and so the fact that the thing flew to the rear was another coincidence.”
About the same mass as the rover itself, the sky crane weighed about 800 kg (1700 lbs) at the time of impact — including 100 kg of fuel — and hit going 100 mph. That’s going to kick up a good-sized plume (although exactly how large has yet to be determined.)
“It was one hell of an impact,” Sell said.
You can watch Steve Sell describe this and other data from the first few days of the MSL mission in the press conference held at JPL on Friday, August 10 below, and follow Sell on his Twitter feed here.
Images: NASA/JPL-Caltech. HiRISE image NASA/JPL/University of Arizona.
At this moment the mega rover Curiosity is barely 48 hours from Mars and transformation into a “priceless asset” on the Red Planet’s surface where she’ll initiate the search for evidence for habitats of Martian microbial life – past or present.
NASA JPL engineers have guided the Curiosity Mars Science Lab (MSL) so precisely on her 352-million-mile (567-million-kilometer) interplanetary journey through space that they decided to cancel today’s planned course adjusting thruster firing, known as Trajectory Correction Maneuver 5 (TCM-5). If needed, they have one last chance for a course correction burn (TCM-6) this weekend on Sunday.
“We are now about 1000 yards from the entry target that will bring us to the touchdown point on the North side of Gale Crater,” said Tomas Martin-Mur, MSL Navigation team chief of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., at an Aug. 2 MSL news briefing.
Curiosity is now less than 450,000 miles away from Mars, careening through space at over 8000 MPH (3576 m/s) and accelerating moment by moment due to the ever increasing pull of Mars gravity.
To put that in perspective, that’s less than twice the distance from the Earth to the Moon.
By the time Curiosity hits the Martian atmosphere on Sunday night/Monday early morning (Aug 5/6) she’ll be blazing through space at more than 13,200 MPH (5,900 m/s).
“I’m less than 500,000 miles from Mars & the Red Planet looks about the size as a full moon seen from Earth. 2 days to landing!” Curiosity tweeted a short while ago.
She remains healthy, with all systems operating nominally. And she is brave!
Curiosity will not flinch knowing she must endure the “7 Minutes of Terror” and the fiery entry,descent and landing to touchdown inside the 96 mile wide Gale Crater just 2 days from now.
Image Caption: Gale Crater Landing site for Curiosity. Credit: NASA
Absolutely staggering photos and science discoveries are expected from Curiosity – the boldest, most daring and by far the most scientifically complex and capable robotic emissary ever dispatched by humans to another world.
But after landing, the team needs to first test the rover’s components and unfurl the robots camera mast and instruments.
“We must recognize that on Sunday night at 10:32 PM PST(1:32 AM EST, 532 GMT) we will have a ‘priceless asset’ that we placed on the surface of another planet that could last for a long time IF we operate it correctly,” said Pete Theisinger, MSL project manager, JPL, at the Aug. 2 news briefing.
“So we will be cautious as hell about what we do with it !”
“This is a very complicated beast, so we all need to exercise caution. It’s much, much more complicated than Spirit and Opportunity in terms of the interactions amongst the various pieces and the things we need to keep track of in order to operate it successfully.”
A few hours after touchdown, Curiosity will send back the first images from the Gale crater landing site beside a towering 3 mile (5 km) high layered Martian mountain, named Mount Sharp.
“We will start doing science right away. Very roughly, the contact science will begin in 2 to 4 weeks. Sampling science will begin 1 to 2 months after we land,” explained Theisinger.
The car-sized Curiosity is 10 feet (3 meters) long and packed with 10 state-of-the-art science experiments that will search for organic molecules – the building blocks of life – and clay minerals, potential markers for signs of Martian microbial life and habitable zones.
Image Caption:Curiosity Mars Science Laboratory Rover – inside the Cleanroom at KSC, with robotic arm extended prior to encapsulation and Nov. 26, 2011 liftoff. Credit: Ken Kremer/kenkremer.com
Watch NASA TV online for live coverage of the Curiosity landing on Aug 5/6 starting at 11:30 pm EDT:
It’s 4 Days to Mars – and NASA’s Curiosity Mars Science Lab (MSL) spacecraft is now flying under the control of the crafts autonomous entry, descent and landing timeline and picking up speed as she plunges ever faster to the Red Planet and her Rendezvous with Destiny.
“Timeline activated. Bleep-bop. I’m running entry, descent & landing flight software all on my own. Countdown to Mars: 5 days,” Curiosity tweeted Tuesday night.
See below an EDL explanatory infographic timeline outlining the critical sequence of events which must unfold perfectly for Curiosity to safely survive the “7 Minutes of Terror” set to begin on the evening of August 5/6.
Aug. 1 TV Viewing Alert – 11:30 PM EDT – see NASA Science Chief John Grunsfeld tonight (Wed, Aug. 1) on the Colbert Report
Image Caption: Curiosity EDL infographic – – click to enlarge
And the excitement is building rapidly for NASA’s biggest, boldest mission ever to the Red Planet as the flight team continues to monitor Curiosity’s onboard systems and flight trajectory. Yesterday, the flight team successfully carried out a memory test on the software for the mechanical assembly that controls MSL’s descent motor, configured the spacecraft for its transition to entry, descent and landing approach mode, and they enabled the spacecraft’s hardware pyrotechnic devices.
Curiosity remains healthy and on course. If fine tuning for the targeted landing ellipse is needed, the next chance to fire on board thrusters to adjust the trajectory is Friday, Aug. 3.
The 4th of 6 possible Trajectory Correction Maneuver (TCM) firings was just accomplished on Sunday, July 29 – details here.
The car sized Curiosity rover is scheduled to touchdown on Mars at about 1:31 a.m. EDT (531 GMT) early on Aug. 6 (10:31 p.m. PDT on Aug. 5) inside Gale Crater and next to a 3 mile (5 km) mountain taller that the tallest in the US.
Gale Crater is 154 km (96 mi) in diameter and dominated by a layered mountain rising some 5 km (3 mi) above the crater floor which exhibits exposures of minerals that may have preserved evidence of past or present Martian life.
Curiosity is packed with 10 state-of-the-art science experiments that will search for organic molecules and clay minerals, potential markers for signs of Martian microbial life and habitable zones.
Watch NASA TV online for live coverage of the Curiosity landing on Aug 5/6:
mars.jpl.nasa.gov or www.nasa.gov
Image Caption: Course correcting thruster firings on July 29 successfully placed Curiosity on target to touchdown beside Mount Sharp inside Gale Crater on Mars on Aug 6 in search of signs of a habitable environment. Credit: NASA
Now just 1 week out from landing beside a 3 mile high (5 km) layered Martian mountain in search of life’s ingredients, aiming thrusters aboard the cruise stage of NASA’s car sized Curiosity Mars Science Lab successfully fired to set the rover precisely on course for a touchdown on Mars at about 1:31 a.m. EDT (531 GMT) early on Aug. 6 (10:31 p.m. PDT on Aug. 5).
Two precise and brief thruster bursts lasting about 7 seconds were successfully carried out just hours ago earlier today at 1 a.m. on July 29, EDT (10 p.m. PDT on July 28). The effect was to change the spacecraft’s velocity by about 1/40 MPH or 1 cm/sec as it smashes into Mars at about 13,200 mph (5,900 meters per second).
This was the fourth and possibly last of 6 interplanetary Trajectory Correction Manuevers (TCM’s) planned by mission engineers to steer Curiosity since departing Earth for the Red Planet.
If necessary, 2 additional TCM’s could be implemented in the final 48 hours next Saturday and Sunday before Curiosity begins plunging into the Martian atmosphere late Sunday night on a do or die mission to land inside the 100 mile wide Gale Crater with a huge mountain in the middle. All 6 TCM maneuvers were preplanned long before the Nov 26, 2011 liftoff from Cape Canaveral, Florida.
Without this course correction firing, MSL would have hit a point at the top of the Martian atmosphere about 13 miles (21 kilometers) east of the target entry point. During the preprogrammed Entry, Descent and Landing (EDL) sequence the vehicle can steer itself in the upper atmosphere to correct for an error amounting to a few miles.
On landing day, MSL can steer enough during its flight through the upper atmosphere to correct for missing the target entry aim point by a few miles and still land on the intended patch of Mars real estate. The mission’s engineers and managers rated the projected 13-mile miss big enough to warrant a correction maneuver.
“The purpose of this maneuver is to move the point at which Curiosity enters the atmosphere by about 13 miles,” said Tomas Martin-Mur of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., chief of the mission’s navigation team. “The first look at telemetry and tracking data afterwards indicates the maneuver succeeded as planned.”
Image Cation: Curiosity Mars Science Laboratory Rover – inside the Cleanroom at KSC, with robotic arm extended prior to encapsulation and Nov. 26, 2011 liftoff. Credit: Ken Kremer/kenkremer.com
As of today (July 30), Curiosity has traveled about 97% of the overall journey to Mars or about 343 million miles (555 million kilometers) of its 352-million-mile (567-million-kilometer) total flight distance.
“I will not be surprised if this was our last trajectory correction maneuver,” Martin Mur said of the TCM-4 firing. “We will be monitoring the trajectory using the antennas of the Deep Space Network to be sure Curiosity is staying on the right path for a successful entry, descent and landing.”
Curiosity will use an unprecedented rocket powered descent stage and a helicopter like sky crane to set down astride the sedimentary layers of Mount Sharp.
She will then conduct a minimum 2 year prime mission with the most sophisticated science instrument package ever dispatched to Mars to determine if a habitable zone ever existed on this region of Mars.
Curiosity will search for the ingredients of life in the form of organic molecules – the carbon based molecules which are the building blocks of life as we know it. The one-ton behemoth is packed to the gills with 10 state of the art science instruments including a 7 foot long robotic arm, scoop, drill and laser rock zapper.
As Curiosity dives down to Mars surface on Aug. 6, 3 spacecraft from NASA and ESA are now positioned in orbit around the Red Planet and are ready to relay and record signals from the “7 Minutes of Terror” – Read the details in my article – here
Watch NASA TV online for live coverage of the Curiosity landing on Aug 5/6:
mars.jpl.nasa.gov or www.nasa.gov
Editor’s note: This guest post was written by Andy Tomaswick, an electrical engineer who follows space science and technology.
One of the most technically difficult tasks of any future manned missions to Mars is to get the astronauts safely on the ground. The combination of the high speed needed for a short trip in space and the much lighter Martian atmosphere creates an aerodynamics problem that has been solved only for robotic spacecraft so far. If people will one day walk Mars’ dusty surface, we will need to develop better Entry Descent and Landing (EDL) technologies first.
Those technologies are part of a recent meeting of the Lunar Planetary Institute (LPI), The Concepts and Approaches for Mars Exploration conference, held June 12-14 in Houston, which concentrated on the latest advances in technologies that might solve the EDL problem.
Of the multitude of technologies that were presented at the meeting, most seemed to involve a multi-tiered system comprising several different strategies. The different technologies that will fill those tiers are partly mission-dependent and all still need more testing. Three of the most widely discussed were Hypersonic Inflatable Aerodynamic Decelerators (HIADs), Supersonic Retro Propulsion (SRP), and various forms of aerobraking.
HIADs are essentially large heat shields, commonly found many types of manned reentry capsule used in the last 50 years of spaceflight. They work by using a large surface area to create enough drag through the atmosphere of a planet to slow the traveling craft to a reasonable speed. Since this strategy has worked so well on Earth for years, it is natural to translate the technology to Mars. There is a problem with the translation though.
HIADs rely on air resistance for its ability to decelerate the craft. Since Mars has a much thinner atmosphere than Earth, that resistance is not nearly as effective at slowing reentry. Because of this drop in effectiveness, HIADs are only considered for use with other technologies. Since it is also used as a heat shield, it must be attached to the ship at the beginning of reentry, when the air friction causes massive heating on some surfaces. Once the vehicle has slowed to a speed where heating is no longer an issue, the HIAD is released in order to allow other technologies to take over the rest of the braking process.
One of those other technologies is SRP. In many schemes, after the HIAD is released, SRP becomes primarily responsible for slowing the craft down. SRP is the type of landing technology commonly found in science fiction. The general idea is very simple. The same types of engines that accelerate the spacecraft to escape velocity on Earth can be turned around and used to stop that velocity upon reaching a destination. To slow the ship down, either flip the original rocket boosters around upon reentry or design forward-facing rockets that will only be used during landing. The chemical rocket technology needed for this strategy is already well understood, but rocket engines work differently when they are traveling at supersonic speeds. More testing must be done to design engines that can deal with the stresses of such velocities. SRPs also use fuel, which the craft will be required to carry the entire distance to Mars, making its journey more costly. The SRPs of most strategies are also jettisoned at some point during the descent. The weight shed and the difficulty of a controlled descent while following a pillar of flame to a landing site help lead to that decision.
Once the SRP boosters fall away, in most designs an aerobraking technology would take over. A commonly discussed technology at the conference was the ballute, a combination balloon and parachute. The idea behind this technology is to capture the air that is rushing past the landing craft and use it to fill a ballute that is tethered to the craft. The compression of the air rushing into the ballute would cause the gas to heat up, in effect creating a hot air balloon that would have similar lifting properties to those used on Earth. Assuming enough air is rushed into the ballute, it could provide the final deceleration needed to gently drop the landing craft off on the Martian surface, with minimal stress on the payload. However, the total amount this technology would slow the craft down is dependent on the amount of air it could inject into its structure. With more air come larger ballute, and more stresses on the material the ballute is made out of. With those considerations, it is not being considered as a stand-alone EDL technology.
These strategies barely scratch the surface of proposed EDL methods that could be used by a human mission to Mars. Curiosity, the newest rover soon set to land on Mars, is using several, including a unique form of SRP known as the Sky Crane. The results of its systems will help scientists like those at the LPI conference determine what suite of EDL technologies will be the most effective for any future human missions to Mars.
Lead image caption: Artist’s concept of Hypersonic Inflatable Aerodynamic Decelerator slowing the atmospheric entry of a spacecraft. Credit: NASA
Second image caption: Supersonic jets are fired forward of a spacecraft in order to decelerate the vehicle during entry into the Martian atmosphere prior to parachute deployment. The image is of the Mars Science Lab at Mach 12 with 4 supersonic retropropulsion jets. Credit: NASA
One of the biggest unknowns for the Mars Science Lab — a.k.a Curiosity — is the landing system, called the Sky Crane, which has never been used before for a spacecraft landing on another planet. It is similar to a sky crane heavy-lift helicopter, and it works like this: after a parachute slows the rover’s descent toward Mars, a rocket-powered backpack will lower the rover on a tether during the final moments before landing. This method allows landing a very large, heavy rover on Mars (instead of the airbag landing systems of previous Mars rovers).
