Category: Missions

NASA’s MESSENGER ? set to become the first spacecraft to orbit the planet Mercury ? launched today at 2:15:56 a.m. EDT aboard a Boeing Delta II rocket from Cape Canaveral Air Force Station, Fla.

The approximately 1.2-ton (1,100-kilogram) spacecraft, designed and built by the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., was placed into a solar orbit 57 minutes after launch. Once in orbit, MESSENGER automatically deployed its two solar panels and began sending data on its status. Once the mission operations team at APL acquired the spacecraft?s radio signals through tracking stations in Hawaii and California, Project Manager David G. Grant confirmed the craft was operating normally and ready for early system check-outs.

?Congratulations to the MESSENGER launch team for a spectacular start to this mission of exploration to the planet Mercury,? said Orlando Figueroa, Deputy Associate Administrator for Programs in the Science Mission Directorate at NASA Headquarters, Washington. ?While we celebrate this major milestone, let?s keep in mind there is still a lot to do before we reach our destination.?

?All the work that went into designing and building this spacecraft is paying off beautifully,? Grant said. ?Now the team is ready to guide MESSENGER through the inner solar system and put us on target to begin orbiting Mercury in 2011.?

During a 4.9-billion mile (7.9-billion kilometer) journey that includes 15 trips around the sun, MESSENGER will fly past Earth once, Venus twice and Mercury three times before easing into orbit around its target planet. The Earth flyby, in August 2005, and the Venus flybys, in October 2006 and June 2007, will use the pull of the planets’ gravity to guide MESSENGER toward Mercury’s orbit. The Mercury flybys in January 2008, October 2008 and September 2009 help MESSENGER match the planet?s speed and location for an orbit insertion maneuver in March 2011. The flybys also allow the spacecraft to gather data critical to planning a yearlong orbit phase.

Since MESSENGER is only the second spacecraft sent to Mercury ? Mariner 10 flew past it three times in 1974-75 and gathered detailed data on less than half the surface ? the mission has an ambitious science plan. With a package of seven science instruments MESSENGER will determine Mercury’s composition; image its surface globally and in color; map its magnetic field and measure the properties of its core; explore the mysterious polar deposits to learn whether ice lurks in permanently shadowed regions; and characterize Mercury’s tenuous atmosphere and Earth-like magnetosphere.

?It took technology more than 30 years, from Mariner 10 to MESSENGER, to bring us to the brink of discovering what Mercury is all about,? said Dr. Sean C. Solomon, MESSENGER?s principal investigator from the Carnegie Institution of Washington, who leads a science team of investigators from 13 institutions across the U.S. ?By the time this mission is done we will see Mercury as a much different planet than we think of it today.?

MESSENGER, short for MErcury Surface, Space ENvironment, Geochemistry, and Ranging, is the seventh mission in NASA’s Discovery Program of lower cost, scientifically focused exploration projects. APL manages the mission for NASA?s Office of Space Science, built the spacecraft and will operate MESSENGER during flight. MESSENGER is the 61st spacecraft built at APL.

?With MESSENGER on its way to Mercury, the reality is sinking in that in a few years, we will see things that no human has ever seen and know infinitely more about the formation of the solar system than we know today,? said Dr. Michael D. Griffin, head of the APL Space Department.

The countdown and launch was managed by the NASA Launch Services Program based at the John F. Kennedy Space Center, Fla. The Delta II launch service was provided by Boeing Expendable Launch Systems, Huntington Beach, Calif. MESSENGER’s science instruments were built by APL; NASA Goddard Space Flight Center, Greenbelt, Md.; University of Michigan, Ann Arbor; and University of Colorado, Boulder. GenCorp Aerojet, Sacramento, Calif., and Composite Optics Inc., San Diego, provided MESSENGER’s propulsion system and composite structure, respectively. KinetX, Inc., Simi Valley, Calif., leads the navigation team. NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the Deep Space Network of antenna stations the team uses to communicate with MESSENGER.

For photos of the launch or more information about the MESSENGER mission visit,

http://messenger.jhuapl.edu or http://www.ksc.nasa.gov

Original Source: NASA News Release

NASA has selected nine studies to investigate new ideas for future mission concepts within its Astronomical Search for Origins Program.

Among the new mission ideas are some that will survey one billion stars within our own galaxy, measure the distribution of galaxies in the distant universe, study dust and gas between galaxies, study organic compounds in space and investigate their role in planetary system formation, and create an optical-ultraviolet telescope to replace the Hubble Space Telescope (HST).

The products from these concept studies will be used for future planning of missions complementing the existing suite of operating missions, including the Hubble and Spitzer Space Telescopes, and developmental missions such as the James Webb Space Telescope and Terrestrial Planet Finder.

Each of the selected studies will have eight months to further develop and refine concepts for missions addressing different aspects of Origins Program science. The Origins Program seeks to address the fundamental questions: “How did we get here?” and “Are we alone?” NASA received 26 proposals in response to this call for mission concepts.

The selected proposals and their principal investigators are:

– BLISS: Revealing the Nature of the Far-IR Universe, Matt Bradford, Jet Propulsion Laboratory, Pasadena, Calif. BLISS will enable far-infrared spectroscopy of the galaxies that make up the far-infrared background out to distances of some of the farthest galaxies known today. BLISS spectral surveys will chart the history of creation of elements heavier than helium and energy production through cosmic time.

– Origins Billion Star Survey (OBSS), Kenneth Johnston, U.S. Naval Observatory, Washington. OBSS will provide a complete census of giant extrasolar planets for all types of stars in our galaxy and the demographics of stars within 30,000 light-years of the sun.

– The Space Infrared Interferometric Telescope (SPIRIT), David Leisawitz, Goddard Space Flight Center, Greenbelt, Md. SPIRIT is an imaging and spectral Michelson interferometer operating in the mid- to far-infrared region of the spectrum. Its very high angular resolution in the far infrared will enable revolutionary developments in the field of star and planet formation research.

– Cosmic Inflation Probe (CIP), Gary Melnick, Smithsonian Astrophysical Observatory, Cambridge, Mass. CIP will measure the shape of cosmic inflation potential by conducting a space-based near-infrared large-area redshift survey capable of detecting galaxies that formed early in the history of the universe.

– HORUS: High ORbit Ultraviolet-visible Satellite, Jon Morse, Arizona State University, Tempe. HORUS will conduct a step-wise, systematic investigation of star formation in the Milky Way, nearby galaxies and the high-redshift universe; the origin of the elements and cosmic structure; and the composition of and physical conditions in the extended atmospheres of extrasolar planets.

– Hubble Origins Probe, Colin Norman, Johns Hopkins University, Baltimore. This mission seeks to combine instruments built for the fifth HST servicing mission: Cosmic Origins Spectrograph and Wide Field Camera 3. This new space telescope at the forefront of modern astronomy will have a unifying focus on the period when the great majority of star and planet formation, heavy element production, black-hole growth and galaxy assembly took place.

– The Astrobiology SPace InfraRed Explorer (ASPIRE) Mission: A Concept Mission to Understand the Role Cosmic Organics Play in the Origin of Life, Scott Sandford, Ames Research Center, Moffett Field, Calif. ASPIRE is an mid- and far-infrared infrared space observatory optimized to spectroscopically detect and identify organic compounds and related materials in space, and understand how these materials are formed, evolve and find their way to planetary surfaces.

– The Baryonic Structure Probe, Kenneth Sembach, Space Telescope Science Institute, Baltimore. The Baryonic Structure Probe will strengthen the foundations of observational cosmology by directly detecting, mapping and characterizing the cosmic web of matter in the early universe, its inflow into galaxies, and its enrichment with elements heavier than hydrogen and helium (the products of stellar and galactic evolution).

– Galaxy Evolution and Origins Probe (GEOP), Rodger Thompson, University of Arizona. GEOP observes more than five million galaxies to study the mass assembly of galaxies, the global history of star formation, and the change of galaxy size and brightness over a volume of the universe large enough to determine the fluctuations of these processes.

More information on NASA’s Origins Program is available on the Internet at:

http://origins.jpl.nasa.gov/

Original Source: NASA News Release

The Swift satellite, which will pinpoint the location of distant yet fleeting explosions that appear to signal the births of black holes, arrived at Kennedy Space Center today in preparation for an October launch.

These enigmatic flashes, called gamma-ray bursts, are the most powerful explosions known in the Universe, emitting more than one hundred billion times the energy than the Sun does in an entire year. Yet they last only a few milliseconds to a few minutes, never to appear in the same spot again.

The Swift satellite is named for the nimble bird, because it can swiftly turn and point its instruments to catch a burst “on the fly” to study both the burst and its afterglow. The afterglow phenomenon follows the initial gamma-ray flash in most bursts; and it can linger in X-ray light, optical light and radio waves for hours to weeks, providing great detail.

“Gamma-ray bursts have ranked among the biggest mysteries in astronomy since their discovery over 35 years ago,” said Dr. Neil Gehrels, Swift Lead Scientist from NASA’s Goddard Space Flight Center in Greenbelt, Md. “Swift is just the right tool needed to solve this mystery. One of Swift’s instruments will detect the burst, while, within a minute, two higher-resolution telescopes will be swung around for an in-depth look. Meanwhile, Swift will ‘e-mail’ scientists and telescopes around the world to observe the burst in real-time.”

The Burst Alert Telescope (BAT) instrument, built by NASA Goddard, will detect and locate about two gamma-ray bursts per week, relaying a 1- to 4-arc-minute position to the ground within about 20 seconds. This position will then be used to “swiftly” re-point the satellite to bring the burst area into the narrower fields of view to study the afterglow with the X-ray Telescope (XRT) and the
UltraViolet/Optical Telescope (UVOT).

These two longer-wavelength (lower-energy) instruments will determine an arc-second position of a burst and the spectrum of its afterglow at visible to x-ray wavelengths. For most of the bursts detected with Swift this data, together with observations conducted with ground-based telescopes, will enable measurement of the redshift, or distance, to the burst source. The afterglow provides crucial information about the dynamics of the burst, but scientists need precise information about the burst in order to locate the afterglow.

Swift notifies the community — which includes museums and the general public, along with scientists at world-class observatories — via the Goddard-maintained Gamma-ray Burst Coordinates Network (GCN). A network of dedicated ground-based robotic telescopes distributed around the world await Swift-GCN alerts.

Continuous burst information flows through the Swift Mission Operations Center, located at Penn State. Penn State, a key U.S. collaborator, built the XRT with University of Leicester (UK) and the Astronomical Observatory of Brera (Italy) and the UVOT with Mullard Space Science Lab (UK).

In addition to providing new clues to the nature of the burst mechanism, Swift’s detection of gamma-ray bursts could provide a bonanza of cosmological data.

“Some bursts likely originate from the farthest reaches, and hence earliest epoch, of the Universe,” said Swift Mission Director John Nousek, professor of astronomy and astrophysics at Penn State. “They act like beacons shining through everything along their paths, including the gas between and within galaxies along the line of sight.”

Theorists have suggested that some bursts may originate from the first generation of stars, and Swift’s unprecedented sensitivity will provide the first opportunity to test this hypothesis.

With NASA’s High-Energy Transient Explorer (HETE-2), now in operation, scientists have determined that at least some bursts involve the explosions of massive stars. Swift will fine-tune this knowledge — that is, answer such questions as how massive, how far, what kind of host galaxies, and why are some bursts so different from others?

While the link between some fraction of bursts with the death of massive stars appears firm, others may signal the merger of neutron stars or black holes orbiting each other in exotic binary star systems. Swift will determine whether there are different classes of gamma-ray bursts associated with a particular origin scenario. Swift may be fast enough to identify afterglows from short bursts, if they exist. Afterglows have only been seen for bursts lasting longer than two seconds. “We may be seeing only half the story so far,” said Gehrels.

The Swift team expects to detect and analyze over 100 bursts a year. When not catching gamma-ray bursts, Swift will conduct an all-sky survey at high-energy “hard” X-ray wavelengths, which will be 20 times more sensitive than previous measurements. Scientists expect that Swift’s enhanced sensitivity relative to earlier surveys will uncover over 400 new supermassive black holes.

Swift, a medium-class explorer mission, is managed by NASA’s Goddard Space Flight Center in Greenbelt, Md., Swift was built in collaboration with national laboratories, universities, and international partners, including the Los Alamos National Laboratory, Penn State University, Sonoma State University, Italy, and the United Kingdom.

Original Source: NASA News Release

Yesterday, 25 July at 09:05 CEST (15:05 local time) the Chinese National Space Administration successfully launched Tan Ce 2, the second of the Double Star science satellites. This marks the latest important milestone in the scientific collaboration between China and the European Space Agency.

Tan Ce (“Explorer”) 2 was launched from the Taiyuan spaceport west of Beijing (Zhangye province) using a Long March 2C rocket. The launch, initially scheduled for today 26 July, took place one day earlier in order to avoid adverse weather conditions expected in the days to come. The spacecraft will join Tan Ce 1, which was launched on 29 December 2003, to complete the Double Star configuration.

About 8 hours after launch the two solid booms holding the magnetometers were successfully deployed. In the next few weeks, all spacecraft sub-systems will be checked out and the commissioning of the on-board scientific instrument will follow.

Double Star will operate alongside ESA?s quartet of Cluster satellites to closely study the interaction between the solar wind and the Earth?s magnetic field. Together, these missions will provide the most detailed view to date. TC-1 is already returning a wealth of scientific data. Back in January, both missions tracked a coronal mass ejection from the Sun and gathered valuable data about the Earth’s bow shock.

Tan Ce 2 reached its nominal orbit, with perigee at 682 km, apogee at 38279 km and inclination of 90.1 deg. The positions and orbit of the Double Star satellites have been carefully defined to enable exploration of the magnetosphere on a larger scale than is possible with Cluster alone. One example of this coordinated activity is the study of the substorms that produce aurorae.

The exact region where these emissions of brightness form is still unclear, but the simultaneous high-resolution measurements combined under these two missions are expected to provide an answer.

ESA is contributing eight scientific instruments to the mission, seven of which are Cluster-derived units.

These are the first ever European experiments to fly on a Chinese satellite. ESA will also be providing ground segment support, four hours each day, via its Villafranca satellite tracking station in Spain.

Scientific cooperation between China and ESA goes back quite a long way. A first Agreement signed back in 1980 facilitated the exchange of scientific information. Thirteen years later, the collaboration focused on a specific mission, Cluster, to study the Earth’s magnetosphere.

Then, in 1997, came a big step forward. The CNSA invited ESA to participate in the Double Star dual-satellite mission to study the Earth?s magnetic field, from a perspective different but complementary to Cluster’s. The Agreement to carry out this joint mission was signed on 9 July 2001 by ESA?s then Director General Antonio Rodot? and CNSA Administrator Luan Enjie.

For Professor David Southwood, ESA?s Science Programme Director: ?Today?s successful launch marks the culmination of these joint efforts and a further important step forward in this historic collaboration between China and Europe.?

Original Source: ESA News Release

NASA today announced the selection of two proposals for detailed study as candidates for the next mission in the agency’s New Frontiers Program.

The proposals are missions that would drop robotic landers into a crater at the south pole of the moon and return samples to Earth, and a mission that would orbit Jupiter from pole to pole for the first time to conduct an in-depth study of the giant planet.

“These two outstanding proposals were judged to be the best science value among the seven submitted to NASA in 2004,” said Dr. Ed Weiler, associate administrator for space science at NASA Headquarters, Washington. “It was a very tough decision, but we’re excited at the prospect of the discoveries either of them could make in continuing our mission of exploration of the solar system, and what they could tell us about our place in the universe,” he added.

Each proposal will now receive up to $1.2 million to conduct a seven-month implementation feasibility study focused on cost, management and technical plans, including educational outreach and small business involvement.

Following detailed mission concept studies, due for submission by March 2005, NASA intends to select one of the mission proposals for full development as the second New Frontiers mission by May 2005. The selected New Frontiers science mission must be ready for launch no later than June 30, 2010, within a mission cost cap of $700 million.

The selected full mission investigations, and the Principal Investigators, are:

– “Moonrise: Lunar South Pole-Aitken Basin Sample Return Mission,” Dr. Michael Duke Principal Investigator, Colorado School of Mines, Boulder. This investigation proposes to land two identical landers on the surface near the moon’s south pole and to return over two kilograms (about five pounds) of lunar materials from a region of the moon’s surface believed to harbor materials from the moon’s mantle.

– “Juno,” Dr Scott Bolton, Principal Investigator, NASA’s Jet Propulsion Laboratory, Pasadena, Calif. This investigation proposes to use a highly instrumented spacecraft placed in a polar orbit about the planet Jupiter to investigate the existence of an ice-rock core, determine the global water and ammonia abundances in Jupiter’s atmosphere, study convection and deep wind profiles in the atmosphere, investigate the origin of the jovian magnetic field, and explore the polar magnetosphere.

The two selected proposals were submitted to NASA in February 2004, in response to the New Frontiers Program 2003 and Missions of Opportunity Announcement of Opportunity.

The New Frontiers Program is designed to provide opportunities to conduct several of the medium-class missions identified as the top priority objectives in the Decadal Solar System Exploration Survey, conducted by the Space Studies Board of the National Research Council.

NASA’s New Horizons mission, which will fly by the Pluto-Charon system in 2014 and then target another Kuiper belt object, was designated the first New Frontiers mission.

Original Source: NASA News Release

One of ESA?s most ambitious current projects has the aim of compiling the most precise map of one thousand million stars in our Galaxy.

Gaia, a spacecraft which will carry two of the most sensitive cameras ever made, is due to be launched in 2010.

It will take five years to detect such a vast quantity of objects, some of which are incredibly faint, and another three years to plot them all in a giant three-dimensional computerised model that shows not only their current position, but their direction of motion, colour and even their composition.

In short, Gaia will produce a completely new view of the Galaxy and everything in it. It will produce the ultimate map, a star catalogue that could be used by every other space mission of the future.

Another exciting aspect of this amazing mission is that it could find objects that we did not know existed – until Gaia turns its supersensitive cameras in their direction. As well as stars, we may find other objects that are very faint, or in areas of the sky where we have not looked in depth yet.

One interesting area of the sky that will be viewed by Gaia is the ?blindspot? found between the Sun and Earth?s orbit.

From Earth, we can only observe this area during the daytime (and even then only on clear days without cloud cover), but it is very hard to pick out small objects such as asteroids, because the Sun?s glare renders them virtually invisible.

These asteroids are sometimes moving near enough to Earth to cause concern, but we may not find out about them until they have moved far enough away from the Sun to be seen by a telescope. One particular large group of asteroids, known as the Atens, spends its time weaving between the Sun and Earth?s orbit.

We know very little about these families of asteroids following the same orbit. They regularly cross the Earth?s orbit, which makes them at least a potential threat, although most of them are not an actual danger to our planet. However, we need to understand why they are there, where they come from and what they are made of.

With the help of its bird?s eye view from space, and its unprecedented accuracy, Gaia is the ideal candidate for keeping track of the Atens, and similar families of asteroids coming close to our home.

But asteroids and Solar System objects will comprise only a tiny fraction of the objects that Gaia will study. Their detection is a by-product of the main goal of Gaia which is to precisely measure the location, motion and composition of several millions of stars in our Galaxy.

Armed with this information we will gain new insight into the life cycle of our Galaxy and its future.

Original Source: ESA News Release

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

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

Image credit: NASA/JHUAPL/SwRI
The Solar Wind Around Pluto (SWAP) instrument aboard the New Horizons spacecraft is designed to measure the interactions of Pluto and Charon with the solar wind, the high-speed stream of charged particles flowing out from the sun. Understanding these interactions will expand researchers’ knowledge of the astrophysical processes affecting these bodies and that part of the solar system.

The space science community understands the extremes (called the bounding states) of solar wind interactions with planets, comets and other bodies, but no one knows what kind of interaction is present at Pluto. Comet Borrelly represents a strong interaction with the solar wind, while Venus represents a weak one.

“We expect solar wind interactions at Pluto to lie somewhere between the strong and weak extremes,” says SWAP Principal Investigator Dr. David J. McComas, a senior executive director at Southwest Research Institute? (SwRI?).

After taking measurements at Pluto, researchers plan to use the SWAP data to define basic parameters about the system. For example, once researchers know how such material comes off Pluto, they can then estimate the amount of Pluto’s atmosphere that escapes into space. This will reveal insights into the structure and destiny of the atmosphere itself.

SWAP would go on to take similar measurements at Charon and at least one Kuiper belt object; however, the team expects those interactions to be much weaker simply because the atmospheres of these objects are expected to be less extensive and not likely to emit much material.

Another of the many Pluto mysteries is where the interactions of the solar wind will occur around the planet, so science plans call for SWAP to take continuous measurements as it nears and passes Pluto.

“We know when and where to use some of the instruments to take an image or a measurement at Pluto,” says McComas. “Solar wind interactions, however, present quite a challenge because we’re trying to measure this invisible thing surrounding Pluto at an uncertain distance from it.”

“The science we expect SWAP to perform is impossible to accomplish without actually going to Pluto-Charon and directly sampling its environment. That capability is something that NASA pioneered and which, to this day, only the United States can do,” says Dr. Alan Stern, principal investigator of New Horizons and an executive director at SwRI.

The incredible distances of Pluto from the sun required that the SWAP team build the largest aperture instrument ever used to measure the solar wind. It allows SWAP to make measurements even when the solar wind is very tenuous. The instrument also combines a retarding potential analyzer (RPA) with an electrostatic analyzer (ESA) to enable extremely fine, accurate energy measurements of the solar wind.

“Should the interaction between Pluto and the solar wind turn out to be very small, the RPA and ESA combination will allow us to measure minute changes in solar wind speed,” says Scott Weidner, the SWAP instrument manager and an SwRI principal scientist.

The various instruments aboard New Horizons were designed and are being built independently, yet they are expected to work together to reveal significant new insights about Pluto, Charon and their Kuiper belt neighbors. SWAP measures low energy interactions, such as those caused by the solar wind. Its complement, the Pluto Energetic Particle Spectrometer Science Investigation, or PEPSSI, will look at higher energy particles, such as pickup ions. The top of SWAP’s energy range can measure some pickup ions, and PEPSSI picks up where SWAP leaves off to see the highest energy interactions.

The sun and its solar wind affect the entire solar system and should create interesting science opportunities for SWAP throughout its planned nine-year voyage to Pluto. SWAP will operate for more than a month each year and will sample heliospheric pickup ions?ions that originate in interstellar space and get ionized when they come near the sun. Other pickup ions come from material inside the solar system. Researchers have shown that even collisions between Kuiper belt objects result in tiny grains that drift toward the sun, evaporate and become ionized. The Cassini spacecraft, when it reaches Saturn this July, will allow researchers to observe
these so-called “outer source” pickup ions to 10 astronomical units (AU, the distance from the Earth to the sun), the region where pickup ions from the outer source are believed to begin.

“We’ll be out to 30 AU before New Horizons even reaches Pluto. While we’re targeting a Kuiper belt object, we could be anywhere from 30 to 50 AU, where the influence of heliospheric pickup ions becomes greater and greater in the solar wind,” says McComas. “On the journey out to Pluto, we’ll be able to validate or disprove the outer source theory, which is an exciting warm up to reaching Pluto itself.”

Original Source: SWRI News Release

Image credit: NASA
One month into the Gravity Probe B mission ? a NASA experiment to test two predictions of Albert Einstein’s Theory of General Relativity ? all spacecraft subsystems continue to perform well, and the spacecraft orbit is stable. . Gravity Probe B is managed by the Marshall Center.

One month into the mission, all spacecraft subsystems are continuing to perform well. The spacecraft’s orbit remains stable and meets our requirements for next month’s transition into the science phase of the mission, upon completion of the spacecraft initialization and orbit checkout. The four gyroscopes are suspended, and we have indications that they are rotating slightly in their housings.

Last weekend, the team successfully performed a procedure to reduce magnetic flux that had built up around the gyroscope rotors (spheres). Magnetic flux is a measure of the number of magnetic field lines penetrating a surface. To ensure that the SQUID readouts receive clean signals from the gyroscopes and to provide the highest possible degree of accuracy during the GP-B science experiment, any magnetic flux around the gyroscope rotors must be minimized.

We reduce magnetic flux by turning on heaters and flowing helium gas, warmed to 10 Kelvin, through the probe. This process also drives off any residual helium remaining in the well of the Dewar, where the probe sits. The flux reduction procedure went smoothly, and when it was completed, the level of trapped flux remaining within the gyros was almost imperceptible. In fact, gyroscope #4, which previously had the highest amount of trapped magnetic flux of all the gyros now has the lowest level.

The flux reduction procedure added heat to the Dewar, thereby increasing the pressure inside to its maximum allowable level. The increased pressure during this stress period caused some of the spacecraft’s micro thrusters to become unstable, resulting in the spacecraft pointing in the wrong direction and triggering a “safemode.”

The 16 micro thrusters are arranged in clusters of four, and local feedback loops within each cluster enable the thrusters to communicate with each other and automatically adjust their flow rates. Ground commands were issued to isolate the unstable thrusters, which resolved the thruster cross-talk issue and enabled the spacecraft to re-orient itself. The thrusters are now functioning properly, the spacecraft’s attitude has been corrected, and it is once again pointing towards the guide star.

The flux reduction operation and subsequent thruster instability and attitude problems has delayed locking the spacecraft onto the guide star, which will be our next major activity. While we have used up some of the contingency days built into the Initialization & Orbit Checkout (IOC) schedule, this phase of the Gravity Probe B mission is still on track for completion within 60 days after launch, at which time the 13-month science data collection will begin. This will be followed by a two-month final calibration of the science instrument assembly.

NASA’s Gravity Probe B mission, also known as GP-B, will use four ultra-precise gyroscopes to test Einstein’s theory that space and time are distorted by the presence of massive objects. To accomplish this, the mission will measure two factors ? how space and time are warped by the presence of the Earth, and how the Earth’s rotation drags space-time around with it.

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