Category: Missions

Image credit: NASA

The launch of NASA’s Space Infrared Telescope Facility (SIRTF) was pushed back at least two days because high seas in the Indian Ocean are delaying a tracking ship from reaching its assigned position. The last of the Great Observatories, SIRTF will now launch on board a Delta 2 rocket no earlier than Monday, August 25 at 0535 GMT (1:35 a.m. EDT). The tracking ship will monitor the Delta 2’s upper stage as it carries SIRTF to a higher orbit after launch. The spacecraft will follow the Earth’s orbit and take pictures of some of the oldest, coldest and dust-obscured objects in the Universe.

The launch of NASA?s Space Infrared Telescope Facility (SIRTF) has been rescheduled to no earlier than Monday, Aug. 25, at 1:35:39 a.m. EDT.

Winter conditions in the southern hemisphere are bringing high wind and high seas delaying the arrival of a tracking and instrumentation ship in the Indian Ocean that is mandatory to support launch. This ship is used to receive data from the Delta second stage. The progress of the ship toward its support location is being monitored. Weather conditions are gradually forecast to improve over the next few days but the arrival time of the ship on station is tentative.

At KSC, the SIRTF Mission Science Briefing has been rescheduled for Friday, Aug. 22 at noon EDT and will be followed by the prelaunch press conference at 1 p.m. EDT.

Original Source: NASA News Release

Image credit: ESA

The launch of the European Space Agency’s SMART-1 mission to explore the Moon was pushed back because of delays with its Ariane 5 launcher. The mission was originally scheduled for August 28, but now it’s been pushed into September. Once SMART-1 does get into space, it will use its ion engine to make larger and larger orbits around the Earth over the course of 16 months until it finally reaches the Moon. It will remain in orbit around the moon for over 2 years analyzing the surface and searching for evidence of water ice near the southern pole.

Europe is going to the Moon for the first time! In just over two weeks the European Space Agency’s (ESA) lunar probe, SMART-1, begins its journey to the Moon. Due to be launched from Kourou in French Guiana on 3rd September (12.04 a.m. 4th September BST) SMART-1 will be powered only by an ion engine which Europe will be testing for the first time as the main spacecraft propulsion. Onboard will be D-CIXS, an X-ray spectrometer built by scientists in the UK, which will provide information on what the Moon is made of.

SMART-1 represents a new breed of spacecraft. It is ESA’s first Small Mission for Advanced Research in Technology – designed to demonstrate innovative and key technologies for future deep space science missions. As well as the ion propulsion mechanism SMART-1 will test miniaturised spacecraft equipment and instruments, a navigation system which in the long term will allow spacecraft to autonomously navigate through the solar system, and a space communication technique whereby SMART-1 will establish a link with the Earth using a laser beam.

Once it has arrived at the Moon (expected to be in January 2005), SMART-1 will perform an unprecedented scientific study of the Moon- providing valuable information which will shed light on some of the unanswered questions. The spacecraft will search for signs of water-ice in craters near the Moon’s poles, provide data on the still uncertain origin of the Moon and reconstruct its evolution by mapping and the surface distribution of minerals and key chemical elements.

Commenting on the mission Prof. Ian Halliday, Chief Executive of PPARC said,” This mission to our only natural satellite is a masterpiece of miniaturisation and UK scientists have played a leading role in providing one of the spacecraft’s key instruments – testament to the UK’s expertise in space science.” Halliday added, “SMART-1 is packed with innovative technology that promises to revolutionise our future exploration of neighbouring planets whilst answering some fundamental questions about the Moon – how did the Moon form and how did it evolve?”

UK scientists have a lead role in the mission. D-CIXS, a compact X-ray Spectrometer, which will make the first ever global X-ray map of the Moon’s surface, has been built by a team led by Principal Investigator Professor Manuel Grande from the CCLRC Rutherford Appleton Laboratory near Oxford. Scientists from a number of other UK institutions are involved in D-CIXS (see notes to editors for further details).

Professor Grande explains how D-CIXS works,

“When the Sun shines on the Moon, its surface fluoresces and D-CIXS will measure the resulting X-rays to determine many of the elements found on its surface. This will provide us with vital clues which will help understand the origins of our Moon.”

Weighing just 4.5 kilograms and the size of a toaster, one of the challenges for the D-CIXS team has been to fit all the necessary components into the instrument. This has been achieved through clever miniaturisation and the development of new technology such as novel X-ray detectors – based on new swept charge devices (similar to the established charged couple devices found in much of today’s technology) and microfabricated collimators with walls no thicker than a human hair.

Lord Sainsbury, Minister for Science and Innovation at the Department of Trade and Industry said:

“SMART-1 is an unprecedented opportunity to provide the most comprehensive study ever of the surface of the Moon. The UK is playing a key role in this important European mission by providing technology that demonstrates excellent collaboration between engineering and science in this country. This mission will also give the European Space Agency the opportunity to develop new technology for future missions, demonstrating once again the effectiveness of joint working between the UK and our European partners in space.”

The European Space Agency’s first spacecraft mission to the Moon, SMART-1, is being prepared for launch at the end of August. The spacecraft was delivered in mid-July to the ESA’s space centre in Kourou, French Guiana, and is expected to launch on August 29. The spacecraft will take 16 months to reach the Moon, following a long spiral trajectory, and using its efficient ion engine to gradually put it into orbit around the Moon. SMART-1 will then search for evidence of water-ice in craters near the Moon’s poles.

Europe?s first probe to the Moon, SMART-1, is about to begin a unique journey that will take it into orbit around our closest neighbour, powered only by an ion engine which Europe will be testing for the first time as main spacecraft propulsion.

The European Space Agency?s SMART-1 spacecraft was delivered to Kourou, French Guiana, on July 15 and is currently being prepared for launch atop an Ariane 5 during the night from August 28 to 29. The launch window will open at 20:04 local time (01:04 on August 29 morning CEST) and will remain open for 26 minutes.

The 367 kg spacecraft will share Ariane?s V162 launch with two commercial payloads: the Indian Space Research Organisation?s Insat 3E and Eutelsat?s e-Bird communication satellites. The smallest spacecraft in the trio, SMART-1, will travel in the lower position, inside a cylindrical adapter, and will be the last to be released.

Europe’s Ariane-5 launcher will put SMART-1 into orbit
A generic Ariane 5 will be in charge of placing these three payloads in a standard geostationary transfer orbit from which each will begin its own journey towards its final operational orbit. SMART-1, powered by its ion engine, will reach its destination in about 16 months, having followed a long spiralling trajectory.

SMART-1?s ion engine will be used to accelerate the probe and raise its orbit until it reaches the vicinity of the Moon, some 350,000 to 400,000 km from Earth. Then, following gravity assists from a series of lunar swingbys in late September, late October and late November 2004, SMART-1 will be ‘captured’ by the Moon?s gravity in December 2004 and will begin using its engine to slow down and reduce the altitude of its lunar orbit.

Testing breakthrough technologies and studying the Moon
SMART-1 is not a standard outer space probe. As ESA?s first Small Mission for Advanced Research in Technology, it is primarily designed to demonstrate innovative and key technologies for future deep space science missions. However, once it has arrived at its destination, it will also perform an unprecedented scientific study of the Moon. SMART-1 is a very small spacecraft (measuring just one cubic metre). Its solar arrays, spanning 14 metres, will deliver 1.9 kW of power, about 75% of which will be used for the probe’s ‘solar electric’ propulsion system.

Close-up view of SMART-1’s stationary plasma thruster
In its role as technological demonstrator, SMART-1?s primary goal is to test this new solar electric propulsion system. This is a form of continuous low-thrust engine that uses electricity derived from solar panels to produce a beam of charged particles that pushes the spacecraft forward. Such engines are commonly called ion engines, and engineers consider them essential for future, long-range space missions. SMART-1 will also test miniaturised spacecraft equipment and instruments, a navigation system that, in the future, will allow spacecraft to autonomously navigate through the solar system, and in addition to a new short-wavelength communication system, a space communication technique by means of which SMART-1 will try to establish a link with the Earth using a laser beam.

Once it enters into a near-polar orbit around the Moon in January 2005, SMART-1 will also become a science platform for lunar observation. SMART-1 will search for signs of water-ice in craters near the Moon?s poles, provide data to shed light on the still uncertain origin of the Moon, and reconstruct its evolution by mapping its topography and the surface distribution of minerals and key chemical elements.

SMART-1 will be the second ESA-led planetary mission to be launched in 2003 after Mars Express in June.

Original Source: ESA News Release

Image credit: NASA/JPL

NASA researchers finally shut down an ion engine that had been running continuously for 30,352 hours. The engine was a duplicate of the one that flew on Deep Space 1, NASA’s mission to test out a range of experimental technologies, and was originally designed to work for 8,000 hours. The engine was finally turned off so that engineers could take it apart to examine the different engine components for wear. Deep Space 1’s engine operated for 16,265 hours.

The future is here for spacecraft propulsion and the trouble-free engine performance that every vehicle operator would like, achieved by an ion engine running for a record 30,352 hours at NASA?s Jet Propulsion Laboratory, Pasadena, Calif.

The engine is a spare of the Deep Space 1 ion engine used during a successful technology demonstration mission that featured a bonus visit to comet Borrelly. It had a design life of 8,000 hours, but researchers kept it running for almost five years, from Oct. 5, 1998, to June 26, 2003, in a rare opportunity to fully observe its performance and wear at different power levels throughout the test. This information is vital to future missions that will use ion propulsion, as well as to current research efforts to develop improved ion thrusters.

“Finding new means to explore our solar system ? rapidly, safely and with the highest possible return on investment ? is a key NASA mission,” said Colleen Hartman, head of Solar System Exploration at NASA Headquarters, Washington, D.C. “Robust in-space flight technologies such as ion propulsion are critical to this effort and will pioneer a new generation of discovery among our neighboring worlds.”

While the engine had not yet reached the end of its life, the decision was made to terminate the test because near-term NASA missions using ion propulsion needed analysis data that required inspection of the different engine components. In particular, the inspection of the thruster?s discharge chamber, where xenon gas is ionized, is critical for mission designers of the upcoming Dawn mission. Dawn, part of NASA’s Discovery Program, will be launched in 2006 to orbit Vesta and Ceres, two of the largest asteroids in the solar system.

“The chamber was in good condition,” said John Brophy, JPL?s project element manager for the Dawn ion propulsion system. “Most of the components showed wear, but nothing that would have caused near-term failure.”

Marc Rayman, former Deep Space 1 project manager, said, ?There are many exciting missions into the solar system that would be unaffordable or truly impossible without ion propulsion. This remarkable test shows that the thrusters have the staying power for long duration missions.?

Ion engines use xenon, the same gas used in photo flash tubes, plasma televisions and some automobile headlights. Deep Space 1 featured the first use of an ion engine as the primary method of propulsion on a NASA spacecraft. That engine was operated for 16,265 hours, the record for operating any propulsion system in space. Ion propulsion systems can be very lightweight, since they can run on just a few grams of xenon gas a day. While the thrust exerted by the engine is quite gentle, its fuel efficiency can reduce trip times and lower launch vehicle costs. This makes it an attractive propulsion system choice for future deep space missions.

“The engine remained under vacuum for the entire test, setting a new record in ion engine endurance testing, a true testament to the tremendous effort and skill of the entire team,” said Anita Sengupta, staff engineer in JPL?s Advanced Propulsion Technology Group. “This unique scientific opportunity benefits current and potential programs.”

“The dedicated work of NASA?s Solar Electric Technology Application Readiness test team, led by JPL, continues to exemplify a commitment to engineering excellence,” said Les Johnson, who leads the In-Space Propulsion Program at NASA?s Marshall Space Flight Center, Huntsville, Ala. “This work, along with significant contributions from NASA?s Glenn Research Center in Cleveland, will take NASA?s space exploration to the next level.”

NASA?s next-generation ion propulsion efforts are led by the In-Space Propulsion Program, managed by the Office of Space Science at NASA Headquarters and implemented by the Marshall Center. The program seeks to develop advanced propulsion technologies that will help near and mid-term NASA science missions by significantly reducing cost, mass or travel times.

Original Source: NASA/JPL News Release

Image credit: NASA/JHU

The first robotic mission to launch to the planet Pluto will be on board an Atlas V rocket, according to NASA. The New Horizons mission, built by NASA, the Southwest Research Institute and Johns Hopkins University is scheduled to take off in January 2006 and wouldn’t reach the planet until 2015. New Horizons will take the first high-resolution photographs of Pluto, and help to answer key questions about its surface, atmosphere, and environment.

NASA has chosen the Atlas V expendable launch vehicle provided by Lockheed Martin Commercial Launch Services, Inc. as the launch system for the proposed Pluto New Horizons mission. The mission is scheduled for launch to Pluto in January 2006. As proposed, the Pluto New Horizons mission is a scientific investigation to obtain the first reconnaissance of Pluto-Charon, a binary planet system.

This will be a firm fixed-price launch service task order awarded under the terms of the current NASA Launch Services contract. The prime contractor will be Lockheed Martin Commercial Launch Services, Inc.; a constituent company of International Launch Services and legal contracting entity for Atlas launch services, located in McLean, Va.

New Horizons would seek to answer key scientific questions regarding the surfaces, atmospheres, interiors, and space environments of Pluto and Charon using imaging, visible and infrared spectral mapping, ultraviolet spectroscopy, radio science, and in-situ plasma sensors. The Principal Investigator is Dr. Alan Stern of the Southwest Research Institute, Boulder, Colo. The implementing institution is the Applied Physics Laboratory of The Johns Hopkins University, Laurel, Md. The proposed mission would use a spacecraft supplied Star 48B based 3rd Stage, manufactured by The Boeing Company of Huntington Beach, Calif., to achieve the required mission performance.

Original Source: NASA News Release

Image credit: NASA/JPL

Engineers at NASA’s Jet Propulsion Lab have built an instrument so sensitive it can measure distances within 1/10th the thickness of a hydrogen atom. This instrument will serve as the heart of NASA’s Space Interferometry Mission, which will be able to detect the interactions between Earth-sized planets and the stars they orbit. Due to launch in 2009, the spacecraft will also measure the distance to stars at an accuracy several hundred times better than currently possible.

Even though astronomers have discovered more than 100 planets around stars other than the Sun in recent years, the “holy grail” of the search — an Earth-sized planet capable of supporting life — remains elusive. The main problem is that an Earthlike planet would be much smaller than any of the gas giants detected so far (see illustration at right).

Planets orbiting other stars are too dim to be observed directly, but scientists infer their presence by the tiny gravitational “wobble” they induce in their parent stars. Observed from tens of light years away (one light-year is 5.88 trillion miles), this movement becomes very tiny indeed. The smaller the planet, the less the star parent wobbles.

To detect the stellar wobble caused by a planet as small as Earth, scientists need an instrument of almost unbelievable sensitivity. Let’s say there’s an astronaut standing on the moon, wiggling her pinky. You’d need an instrument sensitive enough to measure that movement from Earth, a quarter million miles away.

In order to do that, the instrument needs to be a “ruler” accurate to within just one-tenth the width of a hydrogen atom. That’s about 1 millionth of the width of the thickest human hair.

Is such precision possible? After a six-year struggle, engineers at the Jet Propulsion Laboratory recently proved that the answer is yes.

Such sub-atomic measurements were conducted for the first time ever within a vacuum-sealed chamber called the Microarcsecond Metrology Testbed.

By doing this, the engineers proved they can measure the movements of stars with an astonishing degree of accuracy never before achieved in human history.

The testbed, which resembles a shiny silver submarine, is jammed with mirrors, lasers, lenses and other optical components. Because even small air movements can interfere with the measurements, all air is pumped out of the chamber before each experiment is run. Laser beams, moving mirrors and a camera are used to help detect movements of an artificial star, which simulates the light that would be emitted by a real star.

The instrument that engineers have demonstrated in the laboratory will become the heart of a revolutionary new space telescope known as the Space Interferometry Mission.

“Six-and-a-half years ago, this technology was unproven and unsubstantiated,” said Brett Watterson, the mission’s deputy project manager. “It was just a remote possibility that we could do it. It was through ingenuity, insight, leadership and sheer perseverance that the team was able to overcome these difficult technological challenges.”

NASA recently gave the go-ahead for the second stage of development for the mission, which will not only be able to search for Earth-like planets around other stars, but will also measure cosmic distances several hundred times more accurately than currently possible. Scheduled to launch in 2009, it will scan the heavens for five years and provide astronomers with the first truly accurate road map of our Milky Way galaxy.

“This is a historical time that we’re intimately involved with,” Watterson said. “Unlike any other culture in history, we have the technological means, the budget, and the will to determine the occurrence of Earthlike planets orbiting other stars. Everyone on the team is aware of their role in this pivotal stage in the search for life elsewhere in the universe.”

The Space Interferometry Mission is managed by JPL as part of NASA’s Origins program.

Original Source: NASA/JPL News Release

Image credit: NASA/JHU

NASA’s Far Ultraviolet Spectroscopic Explorer (FUSE) satellite got a complete software upgrade this week to improve the precision of its observations. Software engineers from several groups have been working for two years to upgrade the software for the Attitude Control System, the Instrument Data System, and the processor on the Fine Error Sensor guide camera. The new software will even let the observatory work if some or all of its gyroscopes fail.

NASA’s Far Ultraviolet Spectroscopic Explorer (FUSE) satellite was given a new lease on life following the successful implementation of new software in three computers that work together to control the precision pointing of the telescope.

“We have uploaded new flight software, and can operate FUSE with any number of gyroscopes, including none, if the time comes that all of our gyroscopes fail,” said Dr. George Sonneborn, FUSE project scientist from the NASA Goddard Space Flight Center (GSFC), Greenbelt, Md. “This is a significant conceptual and technical development that brings a new tool to the designers of new and existing satellites, and bodes well for continued FUSE operations,” Sonneborn added.

For the past two years, engineers and scientists at the Johns Hopkins University (JHU) in Baltimore, Orbital Sciences Corporation in Dulles, Va., Honeywell Technical Solutions, Inc., Morris Township, N.J., GSFC, and the Canadian Space Agency, Quebec, have worked together to change the flight software used to point the telescope for science observations.

This involved changing the software aboard all three spacecraft computers: the Attitude Control System, the Instrument Data System, and the processor on the Fine Error Sensor guide camera, provided by the Canadian Space Agency. After extensive testing, the new software, for all three computers, was up linked to the satellite in mid-April 2003.

“I would compare this procedure to performing a brain transplant on a living satellite, but it’s more like a triple brain transplant,” said Dr. William Blair, FUSE chief of observatory operations and a research professor at Johns Hopkins University. “All three computers have to talk and work together properly to make it all work,” he said.

Testing on this new configuration has been ongoing since April, even as normal science observations have been carried out. FUSE can operate on as few as zero gyroscopes, with no degradation in science data quality and only a slight loss of observation scheduling efficiency.

The gyroscopes on board FUSE do not move the satellite, but they provide information on how the spacecraft is moving or drifting over time. FUSE has two packages of three ring-laser gyroscopes. Until the new software was loaded, one operating gyroscope on each of the three axes was needed to conduct normal science operations. FUSE still has this needed configuration, but there has been concern about how long the gyroscopes could last. One gyroscope failed in May 2001, and the five remaining gyroscopes all show signs of age.

FUSE has already survived the loss of two of its four reaction wheels in late 2001. The reaction or momentum wheels are devices that normally allow the satellite to be held steady or moved from one pointing direction to another. Through quick thinking, engineers and scientists modified control software to use devices, called magnetic torquer bars, to provide stability in place of the missing reaction wheels. These devices interact with the Earth’s magnetic field to provide a stabilizing effect on the satellite.

The FUSE satellite, launched in June 1999, is a space telescope that performs high-resolution far-ultraviolet spectroscopy of a broad range of astronomical objects. FUSE observes light at shorter wavelengths than the Hubble Space Telescope can observe, thus providing a complementary capability. Because it has survived a number of close calls, but is still returning excellent science data, the team sometimes refers to FUSE as “the little satellite that could.”

Looking ahead, NASA has just released the call for proposals for new observations with the satellite, during its fifth year of operations, by astronomers from around the world.

The JHU manages FUSE for GSFC and the Office of Space Science at NASA Headquarters in Washington. Partners include the JHU Applied Physics Laboratory, the Canadian Space Agency, the French Space Agency, Honeywell Technical Solutions Inc., and primary spacecraft contractor Orbital Sciences Corporation.

Original Source: NASA News Release

Image credit: ESA/NASA

ESA/NASA’s SOHO spacecraft is back to full capacity after a 9-day long blackout. On June 19, the pointing mechanism on the spacecraft’s high-gain antenna malfunctioned; however, controllers were able to retrieve data through its low-gain antenna using larger receiving dishes on Earth. The spacecraft was repositioned this week to let its antenna point directly at Earth. By repositioning it every three months, mission controllers don’t expect they will lose more than a fraction of data, allowing the spacecraft to continue operations for another five years.

ESA/NASA’s solar watchdog, SOHO, is back to full operation after its predicted 9-day-long high-gain antenna blackout. Engineers and scientists are now confident that they understand the situation and can work around it in the future to minimise the data losses.

Since 19 June 2003, SOHO’s high-gain antenna (HGA), which transmits high-speed data to Earth, has been fixed in position following the discovery of a malfunction in its pointing mechanism. This resulted in a loss of signal through SOHO’s usual 26-metre ground stations on 27 June 2003. However, 34-metre radio dishes continued to receive high-speed transmissions from the HGA until 1 July 2003.

Since then, astronomers have been relying primarily on a slower transmission rate signal, sent through SOHO’s backup antenna. It can be picked up whenever a 34-metre dish is available. However, this signal could not transmit all of SOHO’s data. Some data was recorded on board, however, and downloaded using high-speed transmissions through the backup antenna when time on the largest, 70-metre dishes could be spared.

SOHO itself orbits a point in space, 1.5 million kilometres closer to the Sun than the Earth, once every 6 months. To reorient the HGA for the next half of this orbit, engineers rolled the spacecraft through a half-circle on 8 July 2003. On 10 July, the 34-metre radio dish in Madrid re-established contact with SOHO’s HGA. Then on the morning of 14 July 2003, normal operations with the spacecraft resumed through its usual 26-metre ground stations, as predicted.

With the HGA now static, the blackouts, lasting between 9 and 16 days, will continue to occur every 3 months. Engineers will rotate SOHO by 180 degrees every time this occurs. This manoeuvre will minimise data losses. Stein Haugan, acting SOHO project scientist, says “It is good to welcome SOHO back to normal operations, as it proves that we have a good understanding of the situation and can confidently work around it.”

Original Source: ESA News Release

Image credit: NASA

NASA’s Gravity Probe B arrived at Vandenberg Air Force Base on Friday, July 11 to begin launch preparations. Once launched, the spacecraft will use four ultra-precise gyroscopes to test two predictions of Einstein’s General Theory of Relativity: how space and time are warped by the Earth, and how the Earth’s rotation drags space-time around with it. If all goes well, the spacecraft will launch on board a Boeing Delta II rocket in late 2003.

The NASA spacecraft designed to test two predictions of Einstein’s Theory of General Relativity has been shipped from the Lockheed Martin Space Systems Facility in Sunnyvale, Calif., to the launch site at Vandenberg Air Force Base, Calif., after completing environmental testing. The Marshall Center manages the Gravity Probe B program for NASA.

The NASA spacecraft designed to test two important predictions of Albert Einstein’s Theory of General Relativity was shipped yesterday from the Lockheed Martin Space Systems Facility in Sunnyvale, Calif., to the launch site at Vandenberg Air Force Base, Calif., after completing environmental testing.

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.

Stanford University in Stanford, Calif., and Lockheed Martin performed the testing. Shipped by road transport, the vehicle arrived July 10 at Vandenberg for pre-launch operations in anticipation of a launch in late 2003.

NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the GP-B program. NASA’s prime contractor for the mission, Stanford University, conceived the experiment and is responsible for the design and integration of the science instrument, as well as for mission operations and data analysis. Lockheed Martin, a major subcontractor, designed, integrated and tested the spacecraft and some of its major payload components.

The erection of the Boeing Delta II launch vehicle on Space Launch Complex 2 (SLC-2) at Vandenberg Air Force Base is currently scheduled to begin on September 15 with erection of the first stage. Attachment of the nine strap-on solid rocket boosters is scheduled to occur in sets of three on September 16 – 18. The second stage is planned for mating atop the first stage on September 19. Gravity Probe B will be transported from the spacecraft hangar to SLC-2 on October 29 and hoisted atop the second stage. The Delta II fairing will be installed around the spacecraft on November 5, part of final pre-launch preparations. The launch is the responsibility of NASA’s John F. Kennedy Space Center in Florida.

Original Source: NASA News Release

Image credit: ESA

After performing several tests on the troubled SOHO spacecraft, engineers believe they have a solution to ensure that the spacecraft doesn’t have any blackout periods. The pointing mechanism on SOHO’s high-gain antenna malfunctioned on June 27, 2003. Controllers have figured out a way to use larger ground-based receivers which can receive data from the low-gain antenna for a longer period, and receive all the data that SOHO needs to send. Engineers will continue to fix the problem with the high-gain antenna’s motor.

After a number of tests and new insights, SOHO engineers now say there will be no ‘blackout’ periods for SOHO science data.

High-rate transmissions from the Solar and Heliospheric Observatory (SOHO) were initially interrupted on 27 June 2003. The interruption was expected due to a recent malfunction in the pointing mechanism of the spacecraft’s high-gain antenna (HGA). The loss of signal occurred on a 26-metre station of NASA?s Deep Space Network (DSN).

Until 30 June 2003, however, the spacecraft continued beaming down its science data, which were successfully picked up by larger 34-metre DSN stations (when available). In addition, dumping on-board recorder data during these contacts has further reduced data losses so far.

On 30 June 2003, the 70-metre DSN station in Madrid, Spain, successfully received high-rate science data through SOHO’s omnidirectional on-board low-gain antenna. SOHO normally uses this antenna only for low-rate telemetry in emergencies, and the antenna does not need to be repointed.

Successful switch
Even better, when high-rate telemetry was lost on 1 July 2003, during a 34-metre station pass, engineers successfully switched SOHO into a medium-rate telemetry mode, using the low-gain antenna. In medium rate, all real-time science telemetry can be downlinked during station passes. However, on-board recorder dumps are not possible in this mode.

The relatively late occurrence of the initial loss of contact means that the effective SOHO’s HGA antenna beam width is larger than anticipated. Also, since the 34-metre stations are much quieter than the smaller stations, you can use them for longer time periods than expected. Being able to transmit science data through the on-board low-gain antenna using 70- and 34-metre stations therefore means that there will be no hard blackout periods for SOHO science data, given sufficient ground station resources.

Minor losses
However, 34- and 70-metre stations are in higher demand than the 26-metre stations that SOHO normally relies on. Some data losses are therefore expected every day during the 2-3 week periods. “We’re now talking only moderate fractions per day every day during the 2-3 week periods,” says Bernhard Fleck, ESA?s SOHO Project Scientist.

SOHO scientists expect full high-rate telemetry coverage, even on 26-metre stations, to resume on or about 14 July 2003. To achieve this, they will make the spacecraft roll 180? around its Sun-pointing axis in a manoeuvre currently planned for 8 July 2003.

Original Source: ESA News Release