Posted on by Fraser Cain

Update on Gravity Probe B

Image credit: NASA
Gravity Probe B ? a NASA mission to test two predictions of Albert Einstein’s Theory of General Relativity ? is about half way through the initialization and orbit checkout phase of the mission. The mission’s operations team has successfully transmitted over 5,000 commands to the spacecraft, which remains healthy on orbit. Launched from Vandenberg Air Force Base, Calif., Gravity Probe B is managed by the Marshall Center.

On its 52nd day in orbit, the spacecraft continues to be in good health, with all subsystems performing very well. The spacecraft’s orbit, which will remain in full sunlight through August, is stable and meets our requirements for transition into the science phase of the mission. All four gyros are digitally suspended and have passed several very slow-speed calibration tests. Furthermore, the science telescope is locked onto the guide star, IM Pegasi, and we have verified that it is locked onto the correct star

Over the past two weeks, through a combination of software modifications, revised procedures, and commands sent directly to the spacecraft, considerable progress has been made in adjusting the Attitude and Translation Control system (ATC) to properly maintain the spacecraft’s attitude (pitch, yaw, and roll) in orbit. The ATC system accomplishes this important job by controlling the flow of helium gas, continually venting from the Dewar, through the spacecraft’s micro thrusters. This system is critical to the success of the mission because it maintains the required roll rate of the spacecraft, it keeps the spacecraft and science telescope pointed at the guide star, and it keeps the spacecraft in a drag-free orbit. Thus, the team is particularly gratified to now have the ATC functioning reliably, with the science telescope locked onto IM Pegasi.

The “Pegasi” part of the guide star’s name indicates that is located in the constellation Pegasus; the “IM” prefix (as opposed to a Greek letter prefix) indicates that it is a variable star; in fact, it is actually part of a binary star system (one of a pair of stars that closely orbit each other). On a star map, its location coordinates are:

Right Ascension–22 hours 53 minutes 2.27 seconds
Declination–16 degrees 50 minutes 28.3 seconds

IM Peg is about 300 light years from Earth, and its maximum magnitude is 5.85–barely visible to the naked eye. In the Northern Hemisphere, you can view the constellation Pegasus in the evening sky from late August (rises on the Eastern horizon) to early January (sets on the Western horizon).

The process of locking the science telescope onto IM Pegasi started with star trackers on either side of the spacecraft locating familiar patterns of stars. Feedback from the star trackers was used to adjust the spacecraft’s attitude so that it was pointing to within a few degrees of the guide star. The telescope’s shutter was then opened, and a series of increasingly accurate “dwell scans” was performed to home in on the star. Since the spacecraft is rotating along the axis of the telescope, imbalance in the rotation axis can cause the guide star to move in and out of the telescope’s field of view. Feedback from the telescope was sent to the ATC system, which adjusted the spacecraft’s attitude until the guide star remained focused in the telescope throughout multiple spacecraft roll cycles. The ATC was then commanded to “lock” onto the guide star.

Finally, to verify that the telescope was locked onto the correct guide star, the micro thrusters were used to point the spacecraft/telescope at a known neighboring star, HD 216635 (SAO 108242), 1.0047 degrees above IM Pegasi. When the telescope was pointed at this location, the neighboring star appeared with anticipated brightness, and there were no other stars in the immediate vicinity. Thus, the sighting of the star, HD 216635, confirmed the correct relationship between the locations of the two stars, ensuring that the telescope is indeed locked onto the correct guide star. In addition, the telescope has also seen the star HR Peg (HR 8714), a brighter and redder star, located less than half a degree to the left of IM Pegasi.

This past week the team continued performing calibration tests of all gyros, spinning at less than 1 Hz (60 rpm). In addition, the team successfully tested a back-up drag-free mode of the spacecraft with three of the gyros for an entire orbit, and, more significantly, the team completed its first successful test of the primary drag-free mode since re-configuring the micro thrusters, using gyro #3.

In primary drag-free mode, the Gyro Suspension System (GSS) is turned off on one of the gyros, so that no forces are applied to it. The ATC uses feedback from the position of this gyro in its housing to “steer” the spacecraft, keeping the gyro centered. Back-up drag-free mode is similar, but in this case the GSS applies very light forces on the gyro to keep it suspended and centered in its housing. The ATC uses feedback from the GSS to “steer” the spacecraft so that the GSS forces are nullified or canceled, thereby keeping the gyro centered. Applying forces with the GSS to suspend the drag-free gyro adds a very small, but acceptable, amount of noise to the gyro signal, and thus, either primary or back-up drag-free mode can be employed during the science experiment. Upcoming milestones include maintaining the spacecraft in a drag-free orbit, and beginning gyro calibration tests at spin rates of up to 5 Hz (300 rpm).

NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Gravity Probe B program for NASA’s Office of Space Science. Stanford University in Stanford, Calif., developed and built the science experiment hardware and operates the science mission for NASA. Lockheed Martin of Palo Alto, Calif., developed and built the GP-B spacecraft.

Original Source: NASA News Release

Posted on by Fraser Cain

Success for SpaceShipOne!

Image credit: Scaled Composites
The weather was cooperating perfectly in Mojave this morning, as the White Knight carrier airplane lifted off from the runway, cheered on by thousands of space enthusiasts. White Knight circled the airport, steadily rising until it reached an altitude of 15,250 metres (50,000 feet).

And then, at 7:50 am PDT SS1 was released and test pilot Mike Melvill ignited the rubber and nitrous oxide engine and blasted straight up into the sky, experiencing more than 5Gs for just over a minute. Just a few minutes later ground-based radar from several sources confirmed that SS1 had become the first privately built vehicle to reach space.

First a pilot, and now an astronaut, Melvill put SS1’s wings into a position that would guide it into the right trajectory to glide right back where the journey began just an hour earlier: Mojave Airport in California. The return journey took just 25 minutes, and SS1 landed safely.

Although SpaceShipOne reached space today, it wasn’t a qualification flight for the Ansari X Prize, which awards $10 million for the first privately built spacecraft that can carry 3 people to space twice in 2 weeks. On this flight, SS1 only carried the pilot, and it wasn’t officially registered with the X Prize, which requires a month’s notice.

Designer Burt Rutan allayed any fears that it couldn’t make altitude with 3 people, however, warning that Melvill needed to turn the rocket engine off at the right time or he’d be flying to 130 km. Initial reports indicated that this wasn’t necessary on the flight; that the engine might have turned itself off early.

With the success of SS1, official X Prize flights will probably take place before the end of summer. Unless another competitor emerges out of nowhere, SS1 is expected to take the $10 million.

SpaceShipOne has been in development for more than 8 years, even before designer Rutan heard about the X Prize. But for the past few years, billionaire Paul Allen is believed to have invested more than $20 million to get to this point.

Posted on by Fraser Cain

Upcoming Radio Interview

I’ve been listening to the Space Show for the past year or so, and I’ve been really pleased with the quality of guests and topics. You can check out the site here and listen to past archives with literally hundreds of space experts. Well, it’s my turn in the hot seat. Host Dr. David Livingston is going to be interviewing me on Sunday, June 20th at 12:00pm PDT for about 90 minutes. Normally, I’d run out of things to say in a few minutes, but with the release of the Aldridge Report, SpaceShipOne’s launch preparations, and Cassini’s arrival at Saturn, I’m sure we’ll have lots to talk about – after that, I’ll just start making things up. 😉

Here’s a link that explains how and where you can listen to it live, and if you miss the broadcast, you can always listen to it from the archive later.

See you on the radio.

Fraser Cain
Publisher
Universe Today

Posted on by Fraser Cain

Rosetta’s Self Portrait

Image credit: ESA
ESA’s Rosetta comet-chaser has photographed itself in space at a distance of 35 million kilometres from Earth. The CIVA imaging camera system on the Philae lander returned this image as part of its testing in May 2004.

The back of a solar panel is seen here, with contours on the panel are illuminated by sunlight and surfaces of the spacecraft main body are recognisable at lower right.

The CIVA imaging system consists of six identical micro-cameras which will take panoramic pictures of the comet’s surface, when Rosetta arrives at its target in ten years’ time. A spectrometer will also study the composition, texture and albedo (reflectivity) of samples collected from the surface.

Original Source: ESA News Release

Posted on by Fraser Cain

Swirling Cloudtops of Saturn

Image credit: NASA/JPL/Space Science Institute
Saturn?s bright equatorial band displays an exquisite swirl near the planet?s eastern limb. This image was taken with the narrow angle camera on May 18, 2004, from a distance of 23.4 million kilometers (14.5 million miles) from Saturn through a filter sensitive to absorption and scattering of sunlight by methane gas in the infrared (centered at 889 nanometers). The image scale is 139 kilometers (86 miles) per pixel. No contrast enhancement has been performed on this image.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA’s Office of Space Science, Washington, D.C. The imaging team is based at the Space Science Institute, Boulder, Colorado.

For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org.

Posted on by Fraser Cain

Earth Has Blueberries Too

Image credit: University of Utah
Even before marble-shaped pebbles nicknamed ?blueberries? were discovered on Mars by the Opportunity rover, University of Utah geologists studied similar rocks in Utah?s national parks and predicted such stones would be found on the Red Planet.

In a study published in the June 17 issue of the journal Nature, the Utah researchers suggest both the Martian and Utah rocks ? known as hematite concretions ? formed underground when minerals precipitated from flowing groundwater.

?We came up with the ?recipe? for blueberries,? says Marjorie Chan, chair and professor of geology and geophysics at the University of Utah. ?Before Opportunity landed, we thought there might be hematite concretions on Mars. That was based on our study of hematite-rich regions of southern Utah, where hematite balls are found in national parks and have long been a geological oddity that shows up in many rock shops.?

The round rocks are found in southern Utah in Zion and Capitol Reef national parks, Grand Staircase-Escalante National Monument, Snow Canyon State Park and the Moab area.

Their diameters range from one-25th of an inch to 8 inches or more. They are known to New Agers as ?moqui marbles.? Some are the size of small blueberries like those on Mars.

Chan and her colleagues believe the Utah concretions formed perhaps 25 million years ago when minerals precipitated from groundwater flowing through much older Navajo sandstone, the spectacular red rock in southern Utah.

The National Aeronautics and Space Administration?s Opportunity robot rover vehicle landed on Mars? Meridiani Planum on Jan. 25. Five days later, it detected hematite within gray pebbles dotting the landing site, and such pebbles later were spotted embedded in a rock outcrop. Cornell University scientist Steve Squyres, who heads the Opportunity science team, said Feb. 9 the small spheres look ?like blueberries in a muffin? and might be concretions.

In their Nature paper, Chan and colleagues say the Martian ?blueberries? may have formed in a similar manner to those in Utah, namely, when significant volumes of groundwater flowed through permeable rock, and chemical reactions triggered minerals to precipitate and start forming a layered, spherical ball.

?Given the similarities between the marbles in Utah and on Mars, additional scientific scrutiny of the Utah concretions and how they form will probably shed further light on the similar phenomenon on Mars,? University of Washington scientist David Catling wrote in a Nature commentary accompanying the University of Utah study.

The concretions may bear on the search for evidence of past life on Mars because bacteria on Earth can make concretions form more quickly. Chan and colleagues plan to analyze whether there is evidence of past microbial activity in Utah concretions.

Chan conducted the new study with geology graduate student Brenda Beitler and emeritus professor of geology Bill Parry, both at the University of Utah; geologist Jens Ormo of the National Institute of Aerospace Technology in Madrid, Spain; and planetary scientist Goro Komatsu of the International Research School of Planetary Sciences at G. d’Annunzio University in Pescara, Italy.

Martian blueberries and marbles of the spirits
The Utah and Mars hematite concretions have similarities and differences.

In Utah and likely on Mars, ?you have rocks that had iron in them originally,? says Beitler. ?Fluids travel through these rocks and leach out the iron. The water moves through cracks, holes, layers or pores until it reaches some place where the chemistry is different and causes the iron to precipitate out of the water as hematite.?

A major difference is that the Martian ?blueberries? probably are pure hematite ? a form of iron oxide that is gray because it has a larger crystal structure than the reddish form of iron oxide, commonly known as rust. The Utah concretions are mostly sandstone, cemented by hematite that makes up a few percent to perhaps one-third of the rock. The Martian concretions likely precipitated from acidic groundwater. Those in Utah precipitated when hydrocarbon-rich, briny fluids encountered oxygen-rich groundwater.

After the Utah concretions formed in groundwater, the surrounding Navajo sandstone slowly eroded away over millions of years, so the hard, erosion-resistant concretions accumulated on the ground, often in great numbers.

?The loose Utah concretions roll like marbles into depressions, forming ?puddles,? just like their Martian counterparts,? Catling wrote. ?The Hopi Indians have a legend that ?moqui,? or spirits of their ancestors, played games of marbles with the hematite concretions in the American southwest. Although anthropologists discourage use of the word ?moqui? to be respectful to Native Americans, New Age gem collectors sell concretions as ?moqui marbles? and claim that they are endowed with metaphysical powers.?

Hematite, water and life
In 1998, the Mars Global Surveyor orbiting Mars detected what appeared to be a large area of hematite on Meridiani Planum. The broad plain was picked as Opportunity?s landing site because scientists wanted to study the hematite, which almost always forms in water.

Scientists are interested in whether water once existed on Mars (or now exists beneath its surface) because water is necessary for life ? and the possibility of life beyond Earth is one of the great questions long pondered by humanity.

?On Earth, whenever we find water, we find life ? in surface water or underground water, hot water or cold water ? any place there is water on Earth there are microbes, there is life,? says study co-author Bill Parry. ?That?s the bottom line: hematite is linked to life.?

While other evidence from Opportunity suggests there once may have been standing water on Meridiani Planum, the Utah team?s study strongly indicates the Martian ?blueberries? probably formed in groundwater and not in surface water.

?The ?blueberries? easily could have formed in groundwater before there was standing water, if that did exist,? Chan says.

Other scientists previously offered various explanations for Meridiani Planum?s hematite, including that the mineral precipitated in large lakes or in hot springs when Mars? ancient volcanoes were active, or that hematite was left when water leached away other minerals, or that it formed when volcanic ash deposits were altered chemically.

Like Southern Utah, Like Mars
Chan says her team long suspected concretions like those in Utah might be found on Mars. The idea first was suggested by Ormo and Komatsu in a 2003 scientific abstract that got little if any attention. Ormo contacted Chan in spring 2003 and they started collaborating.

The researchers completed a much broader but yet-unpublished study last year indicating that several geological features were seen both in aerial photos of southern Utah?s hematite-rich areas and in images of Mars? hematite regions taken by orbiting spacecraft. These features include large rocky landforms shaped like knobs, pipes and buttes, and places where bleached-looking rock forms white sediment beds or ring-shapes on the surface. Some of the pipes and other features are tens of yards long or wide.

The geologists determined the processes responsible for these large-scale features in Utah involved the flow of briny groundwater saturated with natural gas that bleaches sandstone, and that such groundwater flow, the precipitation of hard hematite-cemented rock and the later erosion of surrounding softer rock also would explain the formation of the erosion-resistant pipes, buttes, knobs and concretions. They concluded a similar process could have formed concretions and larger landforms on Mars.

Chan says studying concretions from Utah and Mars ?will help us learn more about the history of Mars. When we have something to compare it to, it?s a lot easier to figure out.?

Original Source: University of Utah News Release

Posted on by Fraser Cain

Proton Launches Intelsat 10-02

Image credit: ILS
A Russian-built Proton rocket successfully carried the Intelsat 10-02 satellite into orbit today, marking the sixth mission of the year for International Launch Services (ILS).

The Proton M vehicle lifted off from Baikonur?s Pad 39 at 4:27 a.m. today local time (22:27 Wednesday GMT, 6:27 p.m. Wednesday EDT). The rocket?s Breeze M upper stage injected the spacecraft into a geosynchronous transfer orbit about 9 hours and 10 minutes later. The Intelsat 10-02 satellite will be positioned at 359 degrees East longitude (1 degree West), and will provide video, corporate networking, internet and voice services across Europe, Africa, the Middle East, South America and portions of Asia and North America.

ILS, based in McLean, Va., is a joint venture of Lockheed Martin Corp. (NYSE: LMT) of the United States and Khrunichev State Research and Production Space Center of Russia. ILS was formed to market and manage the missions for the Khrunichev Proton and the Lockheed Martin Atlas launch vehicles. ILS? two vehicle families have successfully launched 32 Intelsat satellites over three decades.

?This was another outstanding mission for Proton,? said ILS President Mark Albrecht. ?The Intelsat 10-02 satellite is not only the largest Eurostar E3000 model spacecraft ever built by EADS Astrium, it also is the largest commercial satellite carried by a Proton vehicle. Clearly, Proton?s accuracy and reliability are the reasons it is a vehicle of choice for customers around the world.?

?This successful launch, celebrated during the year of Intelsat?s 40th anniversary, reinforces our historic commitment to delivering the highest quality communications and technology to our customers throughout the world,? said Conny Kullman, CEO of Intelsat Ltd. ?We are grateful to ILS for its efficiency and hard work, which has resulted in our being able to welcome another high-powered satellite to our global fleet.?

Antoine Bouvier, CEO of EADS Astrium, said, ?This is a major event for EADS Astrium, as Intelsat 10-02 is the second Eurostar E3000 model launched by ILS this year. Intelsat 10-02 is also the largest as well as the most powerful satellite ever ordered by Intelsat.?

This was the first of two launches this month for ILS, with the next mission the launch of a U.S. government payload on an Atlas rocket set for June 30. ILS launch teams have been managing campaigns for the two vehicles continuously since last November.

?Between the two launch sites, we have achieved an incredible launch tempo over the last eight months, with eight consecutive successful campaigns thus far and two more in progress,? Albrecht said. ?We expect to continue at this pace the rest of the year.?

ILS has established itself as the indisputable leader of launch services worldwide and offers the industry’s two best launch systems: Atlas and Proton. With a remarkable launch rate of 64 missions during the past three years, the Atlas and Proton launch vehicles have consistently demonstrated the reliability and flexibility that have made them the vehicles of choice. Further demonstrating ILS as the industry leader, ILS has signed more new contracts than its competitors combined over the same three-year period. For more information, visit www.ilslaunch.com.

Posted on by Fraser Cain

Armadillo Completes Test Flight

Image credit: Armadillo Aerospace
The new actuator covers worked out great. We made these by hand, but we also finally got around to getting a sheet metal roll / brake / shear for the shop to make this type of thing easier in the future.

http://media.armadilloaerospace.com/2004_06_15/newCovers.jpg

There was intermittent rain around Dallas today, but we decided to head out to our test site and hope for the best anyway. We taped over all the exposed holes in the vehicle, but it turned out that we only caught a few drops on the way over, and the test site was fine. Since we had a test out there only two and a half weeks ago, we already had some of the gear ready, and we didn?t forget anything this time. We had the vehicle loaded up and ready to go within 30 minutes of arriving.

http://media.armadilloaerospace.com/2004_06_15/loading.jpg

We pressurized the tank to 300 psi, which is a little high for the threaded end closures on these tanks, and we could hear a small pressure leak as the O-ring unloaded a bit.

The engine warmed up predictably, adding further evidence for the benefit of a compressed hot catalyst pack (although we did lose some thrust after compressing it). Something that we noticed this time was that there was still some cloudiness in the exhaust while I brought it up to temperature, but after it had sat for a couple seconds before I started it back up again for the launch it was completely clear. It is likely that there is some path that was channeling enough propellant to self cool at steady state, but after letting it heat soak a bit from the surrounding catalyst, it was uniformly at operating temperature. We can probably use this effect to shorten our warm-ups by warming for a few seconds, then pausing for a couple seconds.

http://media.armadilloaerospace.com/2004_06_15/warming.jpg

I changed the liftoff procedure slightly, opening the valve to the warmup level and holding it there while engaging the boost command. Previously, I would warm the engine, then let it shut completely down for an inertial reset, then just engage boost mode, which pushes the throttle open as fast as it can. This lets more propellant flow into the engine than it would get if there was already chamber pressure, resulting in a brief period of higher than normal thrust and stress. This was quite noticeable in the test on Saturday, which had a momentary kick of nearly one G. Boosting from warmup made the flow completely predictable.

The flight parameters were set for 1.8 seconds of boost, -4 m/s^2 minimum acceleration (slightly more than negative one half G) during the stabilization phase, 3 m/s^2 acceleration in the landing phase, 1 m/s target touchdown velocity, and a 3 m uncertainty margin for the GPS altitude. I increased the minimum acceleration during stabilization because of concerns about throttling the ball valve at small open fractions and low chamber pressures. This wastes more propellant during the flight, but this vehicle can carry so much more propellant than we can use without our burn time waiver that it doesn?t really matter.

The flight was perfect. It went 131 feet high, and landed less than one foot from the launch point.

http://media.armadilloaerospace.com/2004_06_15/perfectBoostedHop.mpg

Analyzing the telemetry told us the following:

This engine didn?t run as well at full throttle with the increased pressure, giving an acceleration during the wide-open-throttle that cycled from 15 to 20 m/s^2. We really need to build a brand new engine to replace this one that has been cut open and modified a half dozen times.

The acceleration prediction that I added to smooth out the hunt-for-acceleration modes helped the stabilize mode, but not as much as it smoothed out the hovering in the test on Saturday. You can clearly hear the pulsations in the flight video. This is understandable, because the flow curve is changing faster at the lower ball valve opening. I should be able to either increase the acceleration prediction, or slow down the ball valve movement at smaller openings. I also realized that I can develop this on the test stand, because hunt-for-chamber-pressure will be effectively the same thing as hunt-for-acceleration on a vehicle.

We knew our chamber pressure signal was messed up, so we didn?t get that in the data logs this time. When we got back to the shop we investigated, and found that the porous pressure snubber in front of the transducer was blocked up. We had this happen once before on a test stand transducer, so we are going to change up from 1 micron to 7 micron filter size. A little bit of peroxide probably starts enough surface corrosion on the 303 SS to clog it up.

The auto-land worked perfectly. I had tried several algorithms on the simulator before settling on this one, and it behaved exactly the same in reality, which is always a pleasant surprise.

We were planning on doing more tests, but the burn time on the first one was 14 seconds, so we really didn?t have much room under the 15 second burn time limit. I could have trimmed the stabilization acceleration and GPS uncertainty, but risking the vehicle to go another 50 feet higher didn?t seem worthwhile, and we called it a day.

http://media.armadilloaerospace.com/2004_06_15/groupPhoto.jpg (Neil, Phil, Tommy, John Carmack, Russ, John Carr, Matt) Joseph was sick today, and James teaches class on Tuesday nights, so they missed it?

We have about 25 hops on this set of jet vanes now, and they have taken on an interesting coloration pattern:

http://media.armadilloaerospace.com/2004_06_15/jetVanes.jpg

We probably won?t fly this vehicle again until we build a completely fresh engine and develop the low throttle hunting algorithm a bit more, but we are submitting some changes to our burn time waiver request to allow us to do initial flights with the small vehicle before flying the big one. It can easily do flights three times as long, which may show up some problems before we hit them with the big vehicle. If the big engine isn?t burned from the leaking valve problem, we should have the big vehicle hovering under the lift this Saturday, so we may be out next Tuesday doing a boosted hop with it.

Speaking of next week? I think Space Ship One has good odds of success in the single-person-to-100km flight. I only see two real issues they may hit: The extended burn above the atmosphere may run into some control issues as the nozzle ablates, which will be hard to correct with only cold gas attitude jets. This would be a fairly benign failure, with the pilot just shutting off the main engine if he can?t hold the trajectory. The dangerous part of the test will be the reentry with a significantly bigger drop than the previous test. At this point, I hope Burt has everything work out and he is able to make the X-Prize flights soon, because our prospects are pretty dim for getting everything working perfectly in the big vehicle in five months and having permission to fly it. I certainly don?t want the insurance company to keep the prize money. If Space Ship One crashes, we will probably throw ourselves at an attempt, but it will be a long shot. No, I don?t think any of the other teams are close.

Original Source: Armadillo Status Report

Posted on by Fraser Cain

Saturn’s Southern Storms

Image credit: NASA/JPL/Space Science Institute
Cassini continues its vigil as Saturn?s atmosphere churns and morphs through time. Four large, dark spots, or storms, form a symmetrical pattern in the mid-southern latitudes as these features squeeze past each other. Further observations will show whether these storms merge or spawn new spots of their own. North of the features, some latitudinal bands exhibit a bumpy or scalloped pattern, probably indicative of planet-scale wave motions in the atmosphere.

The image was taken with the narrow angle camera on May 15, 2004, from a distance of 24.7 million kilometers (15.3 million miles) from Saturn through a filter centered at 750 nanometers. The image scale is 147 kilometers (91 miles) per pixel. Contrast in the image was enhanced to aid visibility.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA’s Office of Space Science, Washington, D.C. The imaging team is based at the Space Science Institute, Boulder, Colorado.

For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org.

Original Source: CICLOPS News Release

Posted on by Fraser Cain

MOST Measures the Pulse of a Star

Image credit: Canadian Space Agency
MOST, Canada?s first space telescope, is shaking up the way astronomers think about stars — and putting a new spin on the life story of our own Sun — by allowing astronomers to see in unprecedented detail how stars shake and spin.

The first results from MOST, a Canadian Space Agency mission which was also the first scientific satellite to be launched by Canada in over 30 years, include the detection of a strong ?pulse? in a young adult star called eta Bootis, and a bad case of stellar acne and hyperactivity in a ?pre-teen? version of the Sun, kappa 1 Ceti. These data offer a unique perspective on what our own Sun may have been like in its youth.

?All this talk of stellar pulses and hyperactivity must sound like ER Meets Star Trek,? admitted MOST Mission Scientist Dr. Jaymie Matthews of the University of British Columbia, who presented the findings today in a keynote address to the annual meeting of the Canadian Astronomical Society in Winnipeg. ?But we really are doing diagnostic check-ups of stars at different points in their lives, by placing them under intensive observation for weeks at a time.?

Matthews made the presentation to a gathering of physicists, astrophysicists, and medical physicists at a unique conference of Canadian physics societies (CAP/CASCA/COMP/BSC CONGRESS 2004) hosted by the Department of Physics and Astronomy at the University of Manitoba in celebration of the Faculty of Science’s 100th anniversary.

These are ambitious results from a Canadian-built and -operated orbiting observatory which is no bigger than a suitcase but can monitor the brightnesses of stars with unmatched precision and thoroughness. MOST, which stands for Microvariability and Oscillations of STars, was launched into orbit last summer and has been collecting data for the last few months.

?MOST is a major advance in the way astronomers study stars, made possible by innovative Canadian technology,? noted Canadian Space Agency President, Dr. Marc Garneau. ?It is the world?s most precise light meter, capable of recording variations as small as one ten thousandth of a percent in the brightness of a star.?

How small is that?

?If all the lights in all the offices of the Empire State Building were on at night,? explains Dr. Garneau, ?you could dim the total light by 1/10,000th of a percent if you pulled down just one window blind by only one centimetre.?

From its vantage point in polar orbit, 820 km high, the tiny MOST space telescope can stare at stars without interruption for up to eight weeks. No other observatory or network of telescopes, including the Hubble, can do this. The unique combination of precision and time coverage enables MOST to look for subtle vibrations in stars that will reveal secrets hidden beneath their surfaces. It also gives MOST the best chance to detect light directly from planets outside our Solar System and study their atmospheres and weather.

MOST is a Canadian Space Agency mission. Dynacon Inc. of Mississauga, Ontario, is the prime contractor for the satellite and its operation, with the University of Toronto Institute for Aerospace Studies (UTIAS) as a major subcontractor. The University of British Columbia (UBC) is the main contractor for the instrument and scientific operations of the MOST mission. MOST is tracked and operated through a global network of ground stations located at UTIAS, UBC and the University of Vienna.

The MOST Canadian space telescope was launched from northern Russia in June 2003 aboard a former Soviet ICBM (Intercontinental Ballistic Missile) converted to peaceful use. Weighing only 54 kg, this suitcase-sized microsatellite is packed with a small telescope and electronic camera to study stellar variability.

One of its early targets was the star eta Bootis, a slightly more massive and younger version of the Sun. Astronomers had picked out this star as one of the best candidates for the new technique of ?asteroseismology? — using surface vibrations to probe the inside of a star, similar to how geophysicists use earthquake vibrations to probe the Earth?s core.

MOST monitored eta Bootis for 28 days without interruption, placing the star under a 24-hour scientific ?stake-out? that revealed behaviour that was hidden from the limited view possible for Earth-bound telescopes. Accumulating almost a quarter of a million individual measurements of this star, MOST reached a level of light-measuring precision at least 10 times better than the best ever achieved before from Earth or space.

The data reveal the star is vibrating, but at a pitch well below the range of human hearing. The stellar melody should allow the MOST team of scientists, including Dr. David Guenther of the Canadian Institute for Computational Astrophysics at St. Mary?s University, Halifax, to determine the age and structure of eta Bootis. ?We?re now in a position to explore new physics in stars, with observations like these,? said Dr. Guenther.

Before observing eta Bootis, while still in the shakedown phase of its mission, MOST was aimed for testing purposes at a fainter star called kappa 1 Ceti. Astronomers already suspected this was a younger version of our Sun, with an age of about 750 million years. The Sun?s age is about 4.5 billion years, and it?s just entering middle age. In terms of a human life, the Sun would be about 45 years old while kappa 1 Ceti would be eight years old ? barely a pre-teen.

Like many human kids, Kappa 1 Ceti is hyperactive, flaring up from time to time, and spinning with much more kinetic energy than sedate older stars like the Sun. It also has a severe case of acne — dark spots on its face which are much larger than those visible on the Sun’s surface. The MOST data, following Kappa 1 Ceti for 29 days, show in exquisite detail how the spots move across the visible side of the star as it spins once every nine days or so. And because a star is not solid, different parts of its gaseous surface spin at different rates. MOST has been able to measure this effect directly in a star other than the Sun for the first time. These results are being prepared for submission to The Astrophysical Journal.

Future targets for MOST include other stars representing the Sun at various stages in its life, and stars known to have giant planets. MOST is designed to be able to register the tiny changes in brightness that will occur as a planet orbits its parent star. The way in which the light changes will tell astronomers about the atmospheric composition of these mysterious worlds, and even if they have clouds.

?It?s like doing a weather report for a planet outside our Solar System,? says Dr. Jaymie Matthews, MOST Mission Scientist, of the University of British Columbia.

Original Source: UBC News Release