Posted on by Fraser Cain

New View of Mars

Image credit: NASA/MSSS

The Mars Global Surveyor spacecraft takes a complete picture of Mars every day to track weather and surface frost across the planet. Surveyor has been tracking the planet this way since 1999, for almost two complete Martian years. This recently released image was taken on May 12, 2003 and shows the northern hemisphere in early autumn and the southern hemisphere in spring. The planet’s four large volcanoes are also visible on the left-hand side.

The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) experiment consists of 3 different cameras: a narrow angle imager that provides the black-and-white high resolution views (up to 1.4 meters per pixel) of Mars, and 2 wide angle cameras, observing in red and blue wavelengths, from which color views of the entire planet are assembled each day. The wide angle cameras provide a daily record of changes in martian weather and surface frost as the seasons progress. MGS MOC has obtained a record of martian weather spanning a little over 2 martian years since it began systematic observations in March 1999.

The view of Mars shown here was assembled from MOC daily global images obtained on May 12, 2003. At that time, the northern hemisphere was in early autumn, and the southern hemisphere in early spring. At the left/center of this view are the four large Tharsis volcanoes: Olympus Mons, Ascraeus Mons, Pavonis Mons, and Arsia Mons. Stretching across the center of the globe is the ~5,000 kilometers (~3,000 miles) long Valles Marineris trough system. The seasonal south polar carbon dioxide frost cap is visible at the bottom of this view. A dust storm sweeps across the plains of northern Acidalia at the upper right. North is up, east is right, sunlight illuminates the planet from the left.

Original Source: MSSS News Release

Posted on by Fraser Cain

Four Astronauts Enter Hall of Fame

Four space shuttle veterans were inducted into the Astronaut Hall of Fame at Florida’s Kennedy Space Center Visitor Complex on Saturday. The newest entrants were Daniel Brandenstein, Robert Gibson, Story Musgrave and Sally Ride (the first American woman in space). The event drew hundreds of people – many were tourists – and actor Lance Henriksen (“The Right Stuff” and “Aliens”) presided over the event. They join 48 astronauts already enshrined at the hall.

Posted on by Fraser Cain

Controllers Delay Beagle 2 Tests

Image credit: ESA

The European Space Agency is in the process of testing various instruments on board the Mars Express spacecraft to make sure everything survived the launch from Earth. One series of tests on the Beagle 2 lander will be postponed until July to give engineers more time to understand a temporary error that occurred in one of Beagle 2’s memory modules. Once they’ve gotten to the bottom of it, ESA will proceed with the formal instrument checks to make sure Beagle 2 is ready for its landing on Mars.

The instruments on board ESA’s mission to Mars, Mars Express, are in the process of being tested to verify that they have survived the launch successfully and will work properly. One of these tests on the Mars Express lander, Beagle 2, has been postponed to the first week of July.

This will give engineers extra time to investigate a temporary anomaly that occurred in a memory unit, the so-called ‘Solid State Mass Memory’ (SSMM). The SSMM stores data from the instruments before sending them to Earth.

This anomaly happened last week during the test of OMEGA, one of Mars Express instruments. For a short period of time, the output of one part of the SSMM contained errors. The problem disappeared spontaneously. The affected memory unit is now working properly. To preserve the data which are stored in this part of the memory, while trying to understand why it occurred, the instrument checks have been rescheduled.

These kind of events are considered routine in a space mission, but engineers would like to understand the causes before re-starting the instrument tests.

Original Source: ESA News Release

Posted on by Fraser Cain

Investigators Strengthen Foam Damage Claim

The Columbia Accident Investigation Board announced today that the foam theory was the “most probable cause” of the space shuttle tragedy. Based on analysis from tons of Columbia debris, they believe there is compelling evidence that a large chunk of foam fell off the fuel tank on launch and cracked a critical heat shield on the shuttle’s wing. Upon re-entry several days later, hot air flowed inside the wing and melted metal braces, and eventually tore the wing off – the entire shuttle came apart moments after that. The investigators are working on their final report, which is due in July.

Posted on by Fraser Cain

Mars Surveyor Snaps Phobos

Image credit: NASA/JPL

NASA’s Mars Global Surveyor took several photos of Mars’ moon Phobos on June 1, 2003. The first image is a low-resolution shot of Phobos about to set behind the Red Planet; while the second, higher resolution image shows incredible details on the moon’s surface. Phobos orbits Mars three times a day at an average distance of only 9,378 kilometres – if you stood on the surface of Phobos, Mars would nearly fill the sky above.

Mars has two natural satellites, or moons, Phobos and Deimos. On 1 June 2003, the Mars Global Surveyor (MGS) spacecraft was slewed eastward to capture these views of the inner moon, Phobos, shortly before it set over the afternoon limb. Phobos orbits Mars about 3 times a day at a distance of about 6,000 km (3,728 mi). About 0.006 times the size of Earth’s Moon, Phobos is a potato-shaped object with dimensions approximately 27 by 22 by 18 kilometers (about 17 by 14 by 11 miles).

The first picture shown here is a color composite of four MGS Mars Orbiter Camera (MOC) wide angle images; the second is the same as the first, but indicates the location of Phobos. The third view is a MOC narrow angle image, taken at the same time as the wide angle views, showing details on the surface of the tiny moon.

Phobos is one of the darkest objects in the Solar System. Thus, four wide angle images were obtained to make the picture of Phobos over the martian limb: a pair of red and blue wide angle images was acquired for the limb, and a pair of separate images were required to see Phobos. The wide angle images illustrate the fact that Phobos is mostly colorless (dark gray); the faint orange/red hue in the wide angle picture is a combination of slight differences in the focal lengths of the blue and red cameras and the orange/red illumination provided by reflection of sunlight off Mars. To a person standing on Phobos, the red planet would fill most of the sky.

The high resolution image (bottom) was taken at the same time as the wide angle views. MGS was about 9,670 kilometers (6,010 miles) from Phobos when the picture was taken. At this distance, the image resolution is about 36 meters (118 ft.) per pixel; the maximum dimension of Phobos as seen in this image (the diagonal from lower left to upper right) is just over 24 km (15 mi). This is the “trailing” hemisphere, the part of Phobos that faces opposite the direction that the moon orbits Mars. This is a part of Phobos that was not seen by MOC in 1998, when MGS made several close flybys of the tiny moon.

The rows of grooves and aligned pits on Phobos are related to, and were probably caused by, a large meteor impact that occurred on the side of Phobos that is not seen here. That large crater, Stickney, was named for the maiden name of the wife of the astronomer that discovered Phobos and the other martian satellite, Deimos, in 1877, Asaph Hall.

Original Source: MSSS News Release

Posted on by Fraser Cain

Opportunity Pushed Back a Day

Image credit: NASA/JPL

NASA decided to push back the launch of the second Mars Explorer rover this week because of a minor problem with its Delta rocket. Engineers decided to replace a protective band of cork insulation on the rocket’s first stage. The time to make this replacement will push back the launch of “Opportunity” to Sunday, June 29 at 0356 GMT (11:56 pm Saturday EDT). If all goes well, Opportunity will follow Spirit, which is already on its way to Mars, and is expected to arrive in early January 2004.

The Flight Readiness Review was held today for the MER-B launch of the ?Opportunity? Mars Exploration Rover. Afterward, a decision was made to postpone the launch by at least a couple of days.

Based on routine post-test inspections, the launch team has elected to remove and replace a band of protective cork insulation on the Delta first stage. The location is below the forward attach points of the strap-on solid rocket boosters. Inspections of a second band located higher on the first stage are being performed.

The time necessary to do this work means a rescheduling of the launch to no earlier than Saturday, June 28 at 11:56:16 p.m. EDT. A firm date will be established on Monday after the engineering team reconvenes.

Original Source: NASA News Release

Posted on by Fraser Cain

Adaptive Optics Improve Images of the Sun

Image credit: NSO

A new adaptive optics system is helping the National Solar Observatory take much more vivid images of the Sun. Earth-based telescopes are limited in resolution by atmospheric distortion, so there was no real point of building them larger than 1.5 metres across – bigger didn’t help. With the new NSO system; however, solar telescopes can now be built 4-metres and larger. This should allow solar astronomers to better understand the processes of solar magnetism and other activities.

Impressive, sharp images of the Sun can be produced with an advanced adaptive optical system that will give new life to existing telescopes and open the way for a generation of large-aperture solar telescopes. This AO system removes blurring introduced by Earth’s turbulent atmosphere and thus provides a clear vision of the smallest structure on the Sun.

The new AO76 system — Adaptive Optics, 76 subapertures — is the largest system designed for solar observations. As demonstrated recently by a team at the National Solar Observatory at Sunspot, NM, AO76 produces sharper images under worse seeing conditions for atmospheric distortion than the AO24 system employed since 1998.

“First light” with the new AO76 system was in December 2002, followed by tests starting in April 2003 with a new high-speed camera that significantly enhanced the system.

“If the first results in late 2002 with the prototype were impressive,” said Dr. Thomas Rimmele, the AO project scientist at the NSO, “I would call the performance that we are getting now truly amazing. I’m quite thrilled with the image quality delivered by this new system. I believe its fair to say that the images we are getting are the best ever produced by the Dunn Solar Telescope.” The Dunn is one of the nation’s premier solar observing facilities.
Dual-purpose program

The new high-order AO system serves two purposes. It will allow existing solar telescopes, like the 76-cm (30-inch) Dunn, to produce higher resolution images and greatly improve their scientific output under a wider range of seeing conditions. It also demonstrates the ability to scale the system up to enable a new generation of large-aperture instruments, including the proposed 4-meter Advanced Technology Solar Telescope (see below) that will see at higher resolutions than current telescopes can achieve.

High resolution observations of the Sun have become increasingly important for solving many of the outstanding problems in solar physics. Studying the physics of flux elements, or solar fine structure in general, requires spectroscopy and polarimetry of the fine structures. The exposures are typically about 1 second long and the resolution currently achieved in spectroscopic/polarimetric data typically is 1 arc-second, which is insufficient for study of fine solar structures. Further, theoretical models predict structures below the resolution limits of 0.2 arc-sec of existing solar telescopes. Observations are needed below the 0.2 arc-sec resolution limit to study the important physical processes that occur on such small scales. Only AO can provide a consistent spatial resolution of 0.1 arc-sec or better from ground based observatories.

AO technology combines computers and flexible optical components to reduce the effects of atmospheric blurring (“seeing”) on astronomical images. Sunspot’s solar AO76 system is based on the Shack-Hartmann correlating technique. In essence, this divides an incoming image into an array of subapertures viewed by a wavefront sensor camera. One subaperture is selected as a reference image. Digital signal processors (DSPs) calculate how to adjust each subaperture to match the reference image. The DSPs then command 97 actuators to reshape a thin, 7.7 cm (3-inch) deformable mirror to cancel much of the blurring. The DSP also can drive a tilt/tip mirror, mounted in front of the AO system, that removes gross image motion caused by the atmosphere.

Closing the loop for sharper images
“A major challenge for astronomers is correcting the light entering their telescopes for the effect of the Earth’s atmosphere,” explained Kit Richards, NSO’s AO lead project engineer. “Air of different temperatures mixing above the telescope makes the atmosphere like a rubber lens that reshapes itself about a hundred times each second.” This is more severe for solar astronomers observing during the day with the Sun heating Earth’s surface, but still causes the stars to twinkle at night.

Further, solar physicists want to study extended bright regions with low contrast. That makes it more challenging for an AO system to correlate the same parts of several slightly different subapertures, and to maintain the correlation from one image frame to the next as the atmosphere changes shape.

(Nighttime astronomy has used a different technique for several years. Lasers generate artificial guide stars in the atmosphere, letting astronomers measure and correct for atmospheric distortion. This is not practical with instruments that observe the Sun.)

In 1998 NSO pioneered use of a low-order AO24 system for solar observations. It has 24 apertures and compensates 1,200 times/second (1,200 Hertz [Hz]). Since August 2000, the team focused on scaling the system up to the high-order AO76 with 76 apertures and correcting twice as fast, 2,500 Hz. The breakthroughs started in late 2002.

First, the servo loop was successfully closed on the new high-order AO system during its first engineering run at the Dunn in December. In a “closed loop” servo system the output is fed back to the input and the errors are driven to 0. An “open loop” system detects the errors and makes corrections but the corrected output is not feed back to the input. The servo system doesn’t know if it is removing all the errors or not. This type of system is faster but very hard to calibrate and keep calibrated. At this point the system used a DALSA camera, which operates at 955 Hz, as the interim wavefront sensor. The optical setup was not finalized and preliminary; “bare-bone” software operated the system.

High-speed wavefront sensor
Even in this preliminary state — intended to demonstrate that the components worked together as a system– and under mediocre seeing conditions, the high-order AO system produced impressive, diffraction-limited images. Time sequences of corrected and uncorrected images show that the new AO system provides fairly consistent high-resolution imaging even as the seeing varies substantially, as is typical for daytime seeing.

Following this milestone, the team installed a new high-speed wavefront sensor camera custom developed for the AO project by Baja Technology and NSO’s Richards. It operates at 2,500 frames/second, which more than doubles the closed-loop servo bandwidth possible with the DALSA camera. Richards also implemented improved control software. In addition, the system was upgraded to drive the tip/tilt correction mirror either directly from the AO wavefront sensor or from a separate correlation/spot tracker system that operates at 3 kHz.

The new high-order AO76 was first tested in April 2003 and immediately started producing excellent images under a wider range of seeing conditions that normally would preclude high-resolution images. The new high-order AO76 was first tested in April 2003 and immediately started producing excellent images under a wider range of seeing conditions that normally would preclude high-resolution images. Striking differences with the AO on versus off are readily visible in images of active areas, granulation, and other features.

“That’s not to say that seeing does not matter anymore,” Rimmele noted. “To the contrary, seeing effects such as anisoplanatism — wavefront differences between the correlation target and the area we want to study — still are limiting factors. But in halfway decent seeing we can lock up on granulation and record excellent images.”

To make large instruments like the Advanced Technology Solar Telescope possible, the high-order AO system will have to be scaled up more than tenfold to at least 1,000 subapertures. And NSO is looking beyond that to a more complex technique, multiconjugate AO. This approach, already being developed for nighttime astronomy, builds a three-dimensional model of the turbulent region rather than treating it as a simple distorted lens.

For now, though, the project team will focus on the completion of the optical setup at the Dunn, installation of the AO bench at the Big Bear Solar Observatory followed by engineering runs, optimization of reconstruction equations and servo loop controls, and characterization of system performance at both sites. Then, the Dunn AO system is to become operational in fall of 2003. The Diffraction Limited Spectro-Polarimeter (DLSP), the main science instrument that can take advantage of the diffraction-limited image quality delivered by the high-order AO, is scheduled for its first commissioning runs in fall of 2003. NSO is developing the DLSP in collaboration with the High Altitude Observatory in Boulder.

Original Source: NSO News Release

Posted on by Fraser Cain

Antenna Problems on SOHO

Image credit: ESA

The NASA/ESA SOHO spacecraft, which observes the Sun, is having problems pointing its high-gain antenna, which it uses to transmit data back to Earth. The cause of the problem hasn’t been figured out yet, but experts think there’s something wrong with its motor or in the gear assembly that steers the antenna – fortunately, its low-gain antenna is still working, so they can still communicate with the spacecraft. If they can’t figure out the problem, SOHO isn’t going to be able to transmit data back as quickly, so there will be blackout periods.

The ESA/NASA SOHO spacecraft, launched in 1995, has been delivering outstanding data about the Sun for over eight years. Recently, however, an anomaly on the pointing mechanism of its high-gain antenna has been recorded.

The high-gain antenna is required to transmit the large amounts of data from SOHO’s scientific observations to Earth. From SOHO’s orbit, the antenna has to be pointed in the proper direction – like a flashlight – for the data to be received at Earth.

The exact nature of the antenna problem is not yet known, but the experts think that a malfunction has occurred in its motor or in the gear assembly that steers the antenna.

SOHO is safe, as the spacecraft has a low-gain antenna, used to control the spacecraft and monitor both spacecraft and instrument health and safety, which remains operational. However, if the high-gain antenna problem persists, there will be periodic losses in the real-time transmission of scientific data of about two and a half weeks each three months. The first blackout is estimated to begin sometime late in the week of 22 June 2003.

A number of options are currently being investigated by the SOHO team to fully recover or minimise any real-time scientific data loss. A joint ESA/NASA press release will follow shortly.

Original Source: ESA News Release

Posted on by Fraser Cain

Stardust Completes Course Correction

Image credit: NASA

NASA’s Stardust probe completed a minor course correction on Thursday, now only 198 days away from its destination: Comet Wild 2. The spacecraft fired its thrusters for 24 minutes and used up nearly 10% of its fuel. Stardust has traveled 2.9 billion kilometres since its launch in 1999, and if all goes well, it will reach the comet in January, 2004 and capture particles from its tail. It will then return the samples to Earth so they can be studied on the ground by scientists.

With 198 days before its historic rendezvous with a comet, NASA’s Stardust spacecraft successfully completed the mission?s third deep space maneuver. This critical maneuver modified the spacecraft?s trajectory, placing it on a path to encounter and collect dust samples from comet Wild 2 in January 2004.

At 2100 Universal Time (2:00 p.m. Pacific Time), Wed., June 18, Stardust fired its eight, 4.4 newton (1 pound) thrusters for a grand total of 1456 seconds, changing the comet sampler?s speed by 34.4 meters per second (about 77 miles per hour). This burn, the second in two days, completed the almost seven-year-long mission?s third deep space maneuver. The June 18 burn required 6.08 kilograms (13.4 pounds) of hydrazine monopropellant to complete. At launch, the spacecraft carried 85 kilograms (187 pounds) of hydrazine propellant.

“It was a textbook maneuver,” said Robert Ryan, Stardust?s mission manager at NASA?s Jet Propulsion Laboratory, Pasadena, Calif. “This was the last big burn we will have prior to our encounter with Wild 2, and it looks very accurate. After sifting through all the post-burn data I expect we will find ourselves right on the money.”

Stardust has traveled over 2.9 billion kilometers (1.8 billion miles) since its February 7, 1999 launch. At present, it is hurtling through the cosmos at 124,300 kilometers per hour (77,200 miles per hour).

In January 2004, Stardust will fly through the halo of dust that surrounds the nucleus of comet Wild 2. The spacecraft will return to Earth in January 2006 to make a soft landing at the U.S. Air Force Utah Test and Training Range. Its sample return capsule, holding microscopic particles of comet and interstellar dust, will be taken to the planetary material curatorial facility at NASA’s Johnson Space Center, Houston, Texas, where the samples will be carefully stored and examined.

Stardust?s cometary and interstellar dust samples will help provide answers to fundamental questions about the origins of the solar system. More information on the Stardust mission is available at http://stardust.jpl.nasa.gov.

Stardust, a part of NASA’s Discovery Program of low-cost, highly focused science missions, was built by Lockheed Martin Astronautics and Operations, Denver, Colo., and is managed by the Jet Propulsion Laboratory, Pasadena, Calif., for NASA’s Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology in Pasadena. The principal investigator is astronomy professor Donald E. Brownlee of the University of Washington in Seattle.

Original Source: NASA News Release

Posted on by Fraser Cain

Nozomi Makes its Earth Flyby

The Japanese space probe Nozomi, passed an important milestone on its journey to Mars Thursday night with the successfully flyby of Earth. The spacecraft passed within 11,000 km of the Earth in order to use our planet’s gravity to assist its trip to Mars. Its challenges aren’t over yet, however, since its heating system still isn’t functional and required in order to enter Mars orbit at the end of its journey. Space experts give Nozomi a 50/50 chance of being able to fix itself before reaching Mars.