Rover to drive off lander base in different directionBY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: January 11, 2004
Engineers now think they'll be ready to roll the Spirit rover off its lander and onto the martian surface early Thursday (Eastern Time), a day later than had been hoped, to accommodate rehearsals and a two-day procedure to rotate the rover into position for its long-awaited egress.
This mosaic image taken by the navigation camera on Spirit produces an overhead view of the rover. The front of Spirit is facing south, or downward, in this view. The yellow arrow illustrates the northwest direction the rover will take during the drive off the lander. Credit: NASA/JPL
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Overnight Saturday, two small explosive devices detonated, cutting cables holding Spirit's two center wheels in place. The rover's robot arm also was released from its launch locks and stowed for roll off. The only physical connection remaining between the rover and its lander is a final umbilical that routes power and data to and from the lander.
That cable will be cut overnight Monday, using the last of more than 120 explosive devices that began detonating Jan. 3 in a precisely scripted sequence beginning with the lander's separation from its cruise stage just before atmospheric entry.
"We are now fully stood up and all of our six wheels are deployed in their normal configuration and they've all been released from the lander," said mission manager Arthur Amador. "So the only thing that we remain in contact with lander is through our umbical."
Otherwise, "the vehicle status remains pretty darn perfect," he said. "Everybody's extremely pleased with the health and safety status of all the subsystems."
Engineers initially hoped to have Spirit roll straight off its lander, almost due south as it sits on the floor of Gusev Crater. But bunched-up airbag material poses a potential threat to the rover's solar arrays and engineers instead have decided to roll off to the northwest. That will require Spirit to rotate in place about 120 degrees to its right.
A model of the Spirit rover rolls off the lander during a test at the Jet Propulsion Laboratory testbed. Credit: NASA/JPL
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First, however, the rover will be commanded to back up eight inches. Then, the four wheels on the outer corners of Spirit's rocker-bogey suspension will be commanded to turn sharply inward. That will cause the rover to rotate about its central axis, literally turning on a dime. Once properly lined up, the rover will roll off the lander's egress aids and onto the surface.
But in keeping with their "brave, but not stupid" approach to Spirit's activation, the JPL engineering team has decided to carry out that rotation in two stages over two days.
To make absolutely sure they understand the rotation and roll-off procedures, engineers plan to spend today testing various commands and techniques using a rover/lander mockup at the Jet Propulsion Laboratory. If no problems surface, the final umbilical will be cut overnight Monday and the rover will be commanded to turn in place about 45 degrees. At that point, pictures and telemetry will be radioed back to Earth for analysis to make sure the procedure is working properly.
The following night - overnight Tuesday U.S. time - Spirit will complete its rotation in two steps. First, it will rotate another 50 degrees, then stop and send back pictures. If all is well, commands will be sent to complete the rotation. That will set the stage for roll off early Thursday U.S. time.
First supernova companion star found
HUBBLE EUROPEAN SPACE AGENCY INFORMATION CENTRE RELEASE
Posted: January 11, 2004
A joint European/University of Hawaii team of astronomers has for the first time observed a stellar "survivor" to emerge from a double star system involving an exploded supernova. Supernovae are some of the most significant sources of chemical elements in the Universe, and they are at the heart of our understanding of the evolution of galaxies.
In this artist's view the red supergiant supernova progenitor star (left) is exploding after having transferred about 10 solar masses of hydrogen gas to the blue companion star (right). This interaction process happened over about 250 years and affected the supernova explosion to such an extent that SN 1993J was later known as one of the most peculiar supernovae ever seen. Credit: ESA and Justyn R. Maund (University of Cambridge)
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Supernovae are some of the most violent events in the Universe. For many years astronomers have thought that they occur in either solitary massive stars (Type II supernovae) or in a binary system where the companion star plays an important role (Type I supernovae). However no one has been able to observe any such companion star. It has even been speculated that the companion stars might not survive the actual explosion.
The second brightest supernova discovered in modern times, SN 1993J, was found in the beautiful spiral galaxy M81 on 28 March 1993. From archival images of this galaxy taken before the explosion, a red supergiant was identified as the mother star in 1993 - only the second time astronomers have actually seen the progenitor of a supernova explosion (the first was SN 1987A, the supernova that exploded in 1987 in our neighbouring galaxy, the Large Magellanic Cloud). Initially rather ordinary, SN 1993J began to puzzle astronomers as its ejecta seemed too rich in the chemical element helium and instead of fading normally it showed a bizarre sharp increase in brightness. The astronomers realised that a normal red supergiant alone could not have given rise to such a weird supernova. It was suggested that the red supergiant orbited a companion star that had shredded its outer layers just before the explosion.
Ten years after this cataclysmic event, a European/University of Hawaii team of astronomers has now peered deep into the glowing remnants of SN 1993J using the NASA/ESA Hubble Space Telescope's Advanced Camera for Surveys (ACS) and the giant Keck telescope on Mauna Kea in Hawaii. They have discovered a massive star exactly at the position of the supernova that is the long sought companion to the supernova progenitor. This is the first supernova companion star ever to be detected and it represents a triumph for the theoretical models. In addition, this observation allows a detailed investigation of the stellar physics leading to supernova explosions. It is now clear that during the last 250 years before the explosion 10 solar masses of gas were torn violently from the red supergiant by its partner. By observing the companion closely in the coming years it may even be possible to detect a neutron star or black hole emerge from the remnants of the explosion "in real time".
Given the paucity of observations of supernova progenitor systems this result, published in Nature on 8 January 2004, is likely to "be crucial to understanding how very massive stars explode and why we see such peculiar supernovae" according to first author Justyn R. Maund from the University of Cambridge, UK.
Stephen Smartt, also from the University of Cambridge, says "Supernova explosions are at the heart of our understanding' of the evolution of galaxies and the formation of chemical elements in the Universe. It is essential that we know what type of stars produce them." For the last ten years astronomers have believed that they could understand the very peculiar behaviour of 1993J by invoking the existence of a binary companion star and now this picture has proved correct.
According to Rolf Kudritzki from the University of Hawaii "The combination of the outstanding spatial resolution of Hubble and the huge light gathering power of the Keck 10m telescope in Hawaii has made this fantastic discovery possible."
Supernovae occur when a star of more than about eight times the mass of the Sun reaches the end of its nuclear fuel reserves and can no longer produce enough energy to keep the star from collapsing under its own immense weight. The core of the star collapses, and the outer layers are ejected in a fast-moving shock wave. This huge energy release causes the visible supernova we see. While astronomers are convinced that observations will match this theoretical model, they are in the embarrassing position that they have confidently identified only two stars that later exploded as supernovae -- the precursors of supernovae 1987A and 1993J.
There have been more than 2000 supernovae discovered in galaxies beyond the Milky Way and there appear to be about eight distinct sub-classes. However identifying which stars produce which flavours has proved incredibly difficult. This team has now embarked on a parallel project with the Hubble Space Telescope to image a large number of galaxies and then wait patiently for a supernova to explode. Supernovae appear in spiral galaxies like M81 on average once every 100 years or so. The team, led by Stephen Smartt, hope to increase the numbers of supernova progenitors known from 2 to 20 over the next five years.
Good morning. Thank You for this thread.
What could cause a hole like that? One mechanism is a rising warm air cell. Normally air cells are invisible, but when conditions are right, such as when thunderheads are building, we can see them by way of associated effects on water vapor. The cell punches through the cloud and air pressure and temperature and humidity combine to allow visible condensation far above the undisturbed cloud layer. In this case the warm air cell would have disallowed condensation.
Wow. These pictures are surely awsome.
