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07.19.2010

Video Camera Will Show Mars Rover's Touchdown

Mars Descent Imager for Curiosity
This Mars Descent Imager (MARDI) camera will fly on the Curiosity rover of NASA's Mars Science Laboratory mission.

A downward-pointing camera on the front-left side of NASA's Curiosity rover will give adventure fans worldwide an unprecedented sense of riding a spacecraft to a landing on Mars.

The Mars Descent Imager, or MARDI, will start recording high-resolution video about two minutes before landing in August 2012. Initial frames will glimpse the heat shield falling away from beneath the rover, revealing a swath of Martian terrain below illuminated in afternoon sunlight. The first scenes will cover ground several kilometers (a few miles) across. Successive images will close in and cover a smaller area each second.

The full-color video will likely spin, then shake, as the Mars Science Laboratory mission's parachute, then its rocket-powered backpack, slow the rover's descent. The left-front wheel will pop into view when Curiosity extends its mobility and landing gear.

The spacecraft's own shadow, unnoticeable at first, will grow in size and slide westward across the ground. The shadow and rover will meet at a place that, in the final moments, becomes the only patch of ground visible, about the size of a bath towel and underneath the rover.

Dust kicked up by the rocket engines during landing may swirl as the video ends and Curiosity's surface mission can begin.

All of this, recorded at about four frames per second and close to 1,600 by 1,200 pixels per frame, will be stored safely into the Mars Descent Imager's own flash memory during the landing. But the camera's principal investigator, Michael Malin of Malin Space Science Systems, San Diego, and everyone else will need to be patient. Curiosity will be about 250 million kilometers (about 150 million miles) from Earth at that point. It will send images and other data to Earth via relay by one or two Mars orbiters, so the daily data volume will be limited by the amount of time the orbiters are overhead each day.

"We will get it down in stages," said Malin. "First we'll have thumbnails of the descent images, with only a few frames at full scale."

Subsequent downlinks will deliver additional frames, selected based on what the thumbnail versions show. The early images will begin to fulfill this instrument's scientific functions.

"I am really looking forward to seeing this movie. We have been preparing for it a long time," Malin said. The lower-resolution version from thumbnail images will be comparable to a YouTube video in image quality. The high-definition version will not be available until the full set of images can be transmitted to Earth, which could take weeks, or even months, sharing priority with data from other instruments.”

The Mars Descent Imager will provide the Mars Science Laboratory team with information about the landing site and its surroundings. This will aid interpretation of the rover's ground-level views and planning of initial drives. Hundreds of the images taken by the camera will show features smaller than what can be discerned in images taken from orbit.

"Each of the 10 science instruments on the rover has a role in making the mission successful," said John Grotzinger of the California Institute of Technology in Pasadena, chief scientist for the Mars Science Laboratory. "This one will give us a sense of the terrain around the landing site and may show us things we want to study. Information from these images will go into our initial decisions about where the rover will go."

The nested set of images from higher altitude to ground level will enable pinpointing Curiosity's location even before an orbiter can photograph the rover on the surface.

Malin said, "Within the first day or so, we'll know where we are and what's near us. MARDI doesn't do much for six-month planning -- we'll use orbital data for that -- but it will be important for six-day and 16-day planning."

In addition, combining information from the descent images with information from the spacecraft's motion sensors will enable calculating wind speeds affecting the spacecraft on its way down, an important atmospheric science measurement. The descent data will later serve in designing and testing future landing systems for Mars that could add more control for hazard avoidance.

After landing, the Mars Descent Imager will offer the capability to obtain detailed images of ground beneath the rover, for precise tracking of its movements or for geologic mapping. The science team will decide whether or not to use that capability. Each day of operations on Mars will require choices about how to budget power, data and time.

Last month, spacecraft engineers and technicians re-installed the Mars Descent Imager onto Curiosity for what is expected to be the final time, as part of assembly and testing of the rover and other parts of the Mars Science Laboratory flight system at NASA's Jet Propulsion Laboratory, Pasadena, Calif. Besides the rover itself, the flight system includes the cruise stage for operations between Earth and Mars, and the descent stage for getting the rover from the top of the Martian atmosphere safely to the ground.

Malin Space Science Systems delivered the Mars Descent Imager in 2008, when NASA was planning a 2009 launch for the mission. This camera shares many design features, including identical electronic detectors, with two other science instruments the same company is providing for Curiosity: the Mast Camera and the Mars Hand Lens Imager.

The company also provided descent imagers for NASA's Mars Polar Lander, launched in 1999, and Phoenix Mars Lander, launched in 2007. However, the former craft was lost just before landing and the latter did not use its descent imager due to concern about the spacecraft's data-handling capabilities during crucial moments just before landing.

Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
Guy.webster@jpl.nasa.gov

2010-239


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This Mars Descent Imager (MARDI) camera will fly on the Curiosity rover of NASA's Mars Science Laboratory mission.Full Size Image
This Mars Descent Imager (MARDI) camera will fly on the Curiosity rover of NASA's Mars Science Laboratory mission.

The downward-looking camera will take about four frames per second at nearly 1,600 by 1,200 pixels per frame for about the final two minutes before Curiosity touches down on Mars in August 2012. Malin Space Science Systems, San Diego, Calif., supplied MARDI and two other camera instruments for the mission. A pocketknife provides scale for the image.

Image Credit: NASA/JPL-Caltech/Malin Space Science Systems
The Mars Descent Imager for NASA's Mars Science Laboratory took this image inside the Malin Space Science Systems clean room in San Diego, Calif., during calibration testing of the camera in June 2008. It shows the instrument's deputy principal investigator, Ken Edgett, holding a six-foot metal ruler that was used as a depth-of-field test target.Full Size Image
The Mars Descent Imager for NASA's Mars Science Laboratory took this image inside the Malin Space Science Systems clean room in San Diego, Calif., during calibration testing of the camera in June 2008. It shows the instrument's deputy principal investigator, Ken Edgett, holding a six-foot metal ruler that was used as a depth-of-field test target. The camera is focused at 7 meters (23 feet) so that everything between about 2 meters (7 feet) and infinity is in focus. This image shows a slightly out-of-focus rock (a rounded cobble of Icelandic basalt with tiny crystals and vesicles) at a distance of about 70 centimeters (2.3 feet), equivalent to the distance the camera will be from the ground after the rover has landed.

Image Credit: NASA/JPL-Caltech/Malin Space Science Systems
This image was taken in the cleanroom where the Curiosity rover is being assembled. It shows the rover, which is about the size of an SUV, hoisted on a white lift, with its black wheels suspended in the air. One engineer is on top of the hoist and is leaning over the rover body, while another is looking up on the ground floor to the right of the rover. Both engineers are wearing white Full Size Image
This graphic portrays the sequence of key events in August 2012 from the time the NASA's Mars Science Laboratory spacecraft, with its rover Curiosity, enters the Martian atmosphere to a moment after it touches down on the surface.

The Mars Descent Imager (MARDI) camera on the rover will provide high-definition video of the descent, looking downward, beginning at the time of heat shield separation. An engineering experiment, the Mars Science Laboratory Entry, Descent and Landing Instrument (MEDLI), will measure atmospheric conditions and the performance of the heat shield on the way down.

The values indicated in this graphic are an example case. The actual timing and altitudes for these events may differ due to differences among the candidate landing sites and unpredictable factors in atmospheric conditions on landing day. For example, the touchdown is indicated in the chart as about 392 seconds after atmospheric entry, but it could be as long as about 480 seconds after entry, depending on which landing site is selected. Also, even for a given site, times for the opening of the parachute could vary by 10 to 15 seconds for a successful landing.

Enclosed inside the capsule formed by the back shell and heat shield, the craft enters the atmosphere at an altitude of about 125 kilometers (78 miles) and a velocity of about 5,800 meters per second (about 13,000 miles per hour).

The parachute deploys about 240 seconds later at an altitude of about 10 kilometers (about 6 miles) and a velocity of about 470 meters per second (about 1,050 miles per hour). After about 28 more seconds, the heat shield separates and drops away at an altitude of about 7 kilometers (about 4 miles) and a velocity of about 160 meters per second (about 360 miles per hour). The rover, with its descent-stage "rocket backpack," is still attached to the back shell on the parachute. The radar on the descent stage begins collecting data about velocity and altitude.

The back shell, with parachute attached, separates from the descent stage and rover about 77 seconds after heat shield separation, about 1.8 kilometers (1.1 miles) above the ground and still rushing toward the ground at about 100 meters per second (about 225 miles per hour). All eight throttleable retrorockets on the descent stage, called Mars landing engines (MLE's), begin firing for the powered descent phase.

Four of the eight engines shut off just before nylon cords begin to spool out to lower the rover from the descent stage for the "sky crane" landing. The rover separates from the descent stage, though still attached by the sky crane bridle, at an altitude of about 20 meters (about 66 feet), with about 12 seconds to go before touchdown. The rover's wheels and suspension system, which double as the landing gear, pop into place just before touchdown at about 0.75 meters per second (about 1.7 miles per hour). When the spacecraft senses touchdown, the connecting cords are severed and the descent stage flies out of the way.

Image Credit: NASA/JPL-Caltech
The Mars Descent Imager for NASA's Mars Science Laboratory took this image in October 2008. The principal investigator for the instrument, Michael Malin of Malin Space Science Systems, San Diego, Calif., lay on the floor beneath the rover for this image.Full Size Image
The Mars Descent Imager for NASA's Mars Science Laboratory took this image in October 2008. The image was taken after the camera was first installed onto the mission’s rover Curiosity inside a clean room at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The principal investigator for the instrument, Michael Malin of Malin Space Science Systems, San Diego, Calif., lay on the floor beneath the rover for this image.

Image Credit: NASA/JPL-Caltech/Malin Space Science Systems

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