Detailed images of Schiaparelli and its descent hardware on Mars

NASA - Mars Reconnaissance Orbiter (MRO) patch / ESA & ROSCOSMOS - ExoMars Mission patch.

27 October 2016

A high-resolution image taken by a NASA Mars orbiter this week reveals further details of the area where the ExoMars Schiaparelli module ended up following its descent on 19 October.

The latest image was taken on 25 October by the high-resolution camera on NASA’s Mars Reconnaissance Orbiter and provides close-ups of new markings on the planet’s surface first found by the spacecraft’s ‘context camera’ last week.

Zooming in on Schiaparelli components on Mars

Both cameras had already been scheduled to observe the centre of the landing ellipse after the coordinates had been updated following the separation of Schiaparelli from ESA’s Trace Gas Orbiter on 16 October. The separation manoeuvre, hypersonic atmospheric entry and parachute phases of Schiaparelli’s descent went according to plan, the module ended up within the main camera’s footprint, despite problems in the final phase.

The new images provide a more detailed look at the major components of the Schiaparelli hardware used in the descent sequence.

The main feature of the context images was a dark fuzzy patch of roughly 15 x 40 m, associated with the impact of Schiaparelli itself. The high-resolution images show a central dark spot, 2.4 m across, consistent with the crater made by a 300 kg object impacting at a few hundred km/h.

The crater is predicted to be about 50 cm deep and more detail may be visible in future images.

The asymmetric surrounding dark markings are more difficult to interpret. In the case of a meteoroid hitting the surface at 40 000­–80 000 km/h, asymmetric debris surrounding a crater would typically point to a low incoming angle, with debris thrown out in the direction of travel.

Schiaparelli landing site

But Schiaparelli was travelling considerably slower and, according to the normal timeline, should have been descending almost vertically after slowing down during its entry into the atmosphere from the west.

It is possible the hydrazine propellant tanks in the module exploded preferentially in one direction upon impact, throwing debris from the planet’s surface in the direction of the blast, but more analysis is needed to explore this idea further

An additional long dark arc is seen to the upper right of the dark patch but is currently unexplained. It may also be linked to the impact and possible explosion.

Finally, there are a few white dots in the image close to the impact site, too small to be properly resolved in this image. These may or may not be related to the impact – they could just be ‘noise’. Further imaging may help identify their origin.

Mars Reconnaissance Orbiter view of Schiaparelli landing site

Some 1.4 km south of Schiaparelli, a white feature seen in last week’s context image is now revealed in more detail. It is confirmed to be the 12 m-diameter parachute used during the second stage of Schiaparelli’s descent, after the initial heatshield entry into the atmosphere. Still attached to it, as expected, is the rear heatshield, now clearly seen.

The parachute and rear heatshield were ejected from Schiaparelli earlier than anticipated. Schiaparelli is thought to have fired its thrusters for only a few seconds before falling to the ground from an altitude of 2–4 km and reaching the surface at more than 300 km/h.

In addition to the Schiaparelli impact site and the parachute, a third feature has been confirmed as the front heatshield, which was ejected about four minutes into the six-minute descent, as planned.

The ExoMars and MRO teams identified a dark spot last week’s image about 1.4 km east of the impact site and this seemed to be a plausible location for the front heatshield considering the timing and direction of travel following the module’s entry.

The mottled bright and dark appearance of this feature is interpreted as reflections from the multilayered thermal insulation that covers the inside of the front heatshield. Further imaging from different angles should be able to confirm this interpretation.

The dark features around the front heatshield are likely from surface dust disturbed during impact.

Zooming in on Schiaparelli landing site

Additional imaging by MRO is planned in the coming weeks. Based on the current data and observations made after 19 October, this will include images taken under different viewing and lighting conditions, which in turn will use shadows to help determine the local heights of the features and therefore a more conclusive analysis of what the features are.

A full investigation is now underway involving ESA and industry to identify the cause of the problems encountered by Schiaparelli in its final phase. The investigation started as soon as detailed telemetry transmitted by Schiaparelli during its descent had been relayed back to Earth by the Trace Gas Orbiter.

The full set of telemetry has to be processed, correlated and analysed in detail to provide a conclusive picture of Schiaparelli’s descent and the causes of the anomaly.

Until this full analysis has been completed, there is a danger of reaching overly simple or even wrong conclusions. For example, the team were initially surprised to see a longer-than-expected ‘gap’ of two minutes in the telemetry during the peak heating of the module as it entered the atmosphere: this was expected to last up to only one minute. However, further processing has since allowed the team to retrieve half of the ‘missing’ data, ruling out any problems with this part of the sequence.

The latter stages of the descent sequence, from the jettisoning of the rear shield and parachute, to the activation and early shut-off of the thrusters, are still being explored in detail. A report of the findings of the investigative team is expected no later than mid-November 2016.

The same telemetry is also an extremely valuable output of the Schiaparelli entry, descent and landing demonstration, as was the main purpose of this element of the ExoMars 2016 mission. Measurements were made on both the front and rear shields during entry, the first time that such data have been acquired from the back heatshield of a vehicle entering the martian atmosphere.

The team can also point to successes in the targeting of the module at its separation from the orbiter, the hypersonic atmospheric entry phase, and the parachute deployment at supersonic speeds, and the subsequent slowing of the module.

These and other data will be invaluable input into future lander missions, including the joint European–Russian ExoMars 2020 rover and surface platform.

Finally, the orbiter is working well and being prepared to make its first set of measurements on 20 November to calibrate its science instruments.

Related article:

Mars Reconnaissance Orbiter Views Schiaparelli Landing Site
http://orbiterchspacenews.blogspot.ch/2016/10/mars-reconnaissance-orbiter-views.html

Related links:

NASA's Mars Reconnaissance Orbiter (MRO): http://www.nasa.gov/mission_pages/MRO/main/index.html

ESA Robotic exploration of Mars: http://exploration.esa.int/

Roscosmos: http://en.federalspace.ru/

ExoMars at IKI: http://exomars.cosmos.ru/

Thales Alenia Space: https://www.thalesgroup.com/en/worldwide/space/space

NASA In 2016 ExoMars orbiter (Electra radio): http://mars.nasa.gov/programmissions/missions/future/exomarsorbiter2016/

Where on Mars?: http://whereonmars.co/

More about...

ExoMars Factsheet: http://www.esa.int/Our_Activities/Space_Science/ExoMars/ExoMars_Factsheet

ExoMars frequently asked questions: http://www.esa.int/Our_Activities/Space_Science/ExoMars/ExoMars_frequently_asked_questions

ExoMars brochure: http://www.esa.int/About_Us/ESA_Publications/ESA_Publications_Brochures/ESA_BR-327_EXOMARS_2016

Images, Text, Credits: European Space Agency (ESA)/Markus Bauer/NASA/JPL-Caltech/MSSS/University of Arizona.

Best regards, Orbiter.ch

Accompanying satellite launched from Tiangong-2

CASC - Shenzhou-11 Mission patch.

26 October 2016

An accompanying satellite was launched from space lab Tiangong-2 at 7:31 a.m. on Oct. 23，2016, said Chinese scientists.

The satellite, which weighs 47 kilograms and is the size of a printer, was launched into space aboard Tiangong-2 on Sept. 15, said the Technology and Engineering Center for Space Utilization under the Chinese Academy of Sciences.

The micro satellite is able to conduct efficient orbit control, process tasks autonomously and transmit data at high speeds, with stronger capabilities compared with the accompanying satellite of the Shenzhou-7 spacecraft, it said.

At the end of October, the satellite will orbit close to Tiangong-2 and Shenzhou-11 and take photos with the high-resolution camera installed on it.

The accompanying satellite will also carry out space experiments with Tiangong-2 to expand the use of space.

The Shenzhou-11 spacecraft carried two astronauts into space on Oct. 17 from northwest China's Gobi Desert. It docked with Tiangong-2 six days later.

For more information, visit:

http://www.cnsa.gov.cn/n6443408/index.html
http://english.spacechina.com/n16421/index.html

Image, Text, Credits: CASC/Xinhua/News.cn.

Best regards, Orbiter.ch

NASA's Juno Mission Exits Safe Mode, Performs Trim Maneuver

NASA - JUNO Mission logo.

Oct. 26, 2016

NASA’s Juno spacecraft at Jupiter has left safe mode and has successfully completed a minor burn of its thruster engines in preparation for its next close flyby of Jupiter.

Mission controllers commanded Juno to exit safe mode Monday, Oct. 24, with confirmation of safe mode exit received on the ground at 10:05 a.m. PDT (1:05 p.m. EDT). The spacecraft entered safe mode on Oct. 18 when a software performance monitor induced a reboot of the spacecraft's onboard computer. The team is still investigating the cause of the reboot and assessing two main engine check valves.

"Juno exited safe mode as expected, is healthy and is responding to all our commands,” said Rick Nybakken, Juno project manager from NASA's Jet Propulsion Laboratory in Pasadena, California. "We anticipate we will be turning on the instruments in early November to get ready for our December flyby."

Image above: This artist's rendering shows NASA's Juno spacecraft making one of its close passes over Jupiter. Image Credit: NASA.

In preparation for that close flyby of Jupiter, Juno executed an orbital trim maneuver Tuesday at 11:51 a.m. PDT (2:51 p.m. EDT) using its smaller thrusters. The burn, which lasted just over 31 minutes, changed Juno’s orbital velocity by about 5.8 mph (2.6 meters per second) and consumed about 8 pounds (3.6 kilograms) of propellant. Juno will perform its next science flyby of Jupiter on Dec. 11, with time of closest approach to the gas giant occurring at 9:03 a.m. PDT (12:03 p.m. EDT). The complete suite of Juno’s science instruments, as well as the JunoCam imager, will be collecting data during the upcoming flyby.

“We are all excited and eagerly anticipating this next pass close to Jupiter,” said Scott Bolton, principal investigator of Juno from the Southwest Research Institute in San Antonio. “The science collected so far has been truly amazing."

The Juno spacecraft launched on Aug. 5, 2011, from Cape Canaveral, Florida, and arrived at Jupiter on July 4, 2016. During its mission of exploration, Juno soars low over the planet's cloud tops -- as close as about 2,600 miles (4,100 kilometers). During these flybys, Juno probes beneath the obscuring cloud cover of Jupiter and studies its auroras to learn more about the planet's origins, structure, atmosphere and magnetosphere.

More information on the Juno mission is available at: http://www.nasa.gov/juno

The public can follow the mission on Facebook and Twitter at:

http://www.facebook.com/NASAJuno

http://www.twitter.com/NASAJuno

Images and information on how members of the public can participate in JunoCam’s mission, can be found at:  http://www.missionjuno.swri.edu/junocam

Image (mentioned), Text, Credits: NASA/Dwayne Brown/Laurie Cantillo/Tony Greicius/JPL/DC Agle.

Greetings, Orbiter.ch

ESO’s VLT Detects Unexpected Giant Glowing Halos around Distant Quasars

ESO - European Southern Observatory logo.

26 October 2016

Bright halos around distant quasars

An international team of astronomers has discovered glowing gas clouds surrounding distant quasars. This new survey by the MUSE instrument on ESO’s Very Large Telescope indicates that halos around quasars are far more common than expected. The properties of the halos in this surprising find are also in striking disagreement with currently accepted theories of galaxy formation in the early Universe.

An international collaboration of astronomers, led by a group at the Swiss Federal Institute of Technology (ETH) in Zurich, Switzerland, has used the unrivalled observing power of MUSE on the Very Large Telescope (VLT) at ESO’s Paranal Observatory to study gas around distant active galaxies, less than two billion years after the Big Bang. These active galaxies, called quasars, contain supermassive black holes in their centres, which consume stars, gas, and other material at an extremely high rate. This, in turn, causes the galaxy centre to emit huge amounts of radiation, making quasars the most luminous and active objects in the Universe.

Bright halos around distant quasars

The study involved 19 quasars, selected from among the brightest that are observable with MUSE. Previous studies have shown that around 10% of all quasars examined were surrounded by halos, made from gas known as the intergalactic medium. These halos extend up to 300 000 light-years away from the centres of the quasars. This new study, however, has thrown up a surprise, with the detection of large halos around all 19 quasars observed  — far more than the two halos that were expected statistically. The team suspects this is due to the vast increase in the observing power of MUSE over previous similar instruments, but further observations are needed to determine whether this is the case.

“It is still too early to say if this is due to our new observational technique or if there is something peculiar about the quasars in our sample. So there is still a lot to learn; we are just at the beginning of a new era of discoveries”, says lead author Elena Borisova, from the ETH Zurich.

The original goal of the study was to analyse the gaseous components of the Universe on the largest scales; a structure sometimes referred to as the cosmic web, in which quasars form bright nodes [1]. The gaseous components of this web are normally extremely difficult to detect, so the illuminated halos of gas surrounding the quasars deliver an almost unique opportunity to study the gas within this large-scale cosmic structure.

3D animation of quasar halo

The 19 newly-detected halos also revealed another surprise: they consist of relatively cold intergalactic gas — approximately 10 000 degrees Celsius. This revelation is in strong disagreement with currently accepted models of the structure and formation of galaxies, which suggest that gas in such close proximity to galaxies should have temperatures upwards of a million degrees.

The discovery shows the potential of MUSE for observing this type of object [2]. Co-author Sebastiano Cantalupo is very excited about the new instrument and the opportunities it provides: “We have exploited the unique capabilities of MUSE in this study, which will pave the way for future surveys. Combined with a new generation of theoretical and numerical models, this approach will continue to provide a new window on cosmic structure formation and galaxy evolution.”

Notes:

[1] The cosmic web is the structure of the Universe at the largest scale. It is comprised of spindly filaments of primordial material (mostly hydrogen and helium gas) and dark matter which connect galaxies and span the chasms between them. The material in this web can feed along the filaments into galaxies and drive their growth and evolution.

[2] MUSE is an integral field spectrograph and combines spectrographic and imaging capabilities. It can observe large astronomical objects in their entirety in one go, and for each pixel measure the intensity of the light as a function of its colour, or wavelength.

More information:

This research was presented in the paper "Ubiquitous giant Lyα nebulae around the brightest quasars at z ~ 3.5 revealed with MUSE", to appear in the Astrophysical Journal.

The team is composed of Elena Borisova, Sebastiano Cantalupo, Simon J. Lilly, Raffaella A. Marino and Sofia G. Gallego (Institute for Astronomy, ETH Zurich, Switzerland), Roland Bacon and Jeremy Blaizot (University of Lyon, Centre de Recherche Astrophysique de Lyon, Saint-Genis-Laval, France), Nicolas Bouché (Institut de Recherche en Astrophysique et Planétologie, Toulouse, France), Jarle Brinchmann (Leiden Observatory, Leiden, The Netherlands; Instituto de Astrofísica e Ciências do Espaço, Porto, Portugal), C Marcella Carollo (Institute for Astronomy, ETH Zurich, Switzerland), Joseph Caruana (Department of Physics, University of Malta, Msida, Malta; Institute of Space Sciences & Astronomy, University of Malta, Malta), Hayley Finley (Institut de Recherche en Astrophysique et Planétologie, Toulouse, France), Edmund C. Herenz (Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany), Johan Richard (Univ Lyon, Centre de Recherche Astrophysique de Lyon, Saint-Genis-Laval, France), Joop Schaye and Lorrie A. Straka (Leiden Observatory, Leiden, The Netherlands), Monica L. Turner (MIT-Kavli Center for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA), Tanya Urrutia (Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany), Anne Verhamme (University of Lyon, Centre de Recherche Astrophysique de Lyon, Saint-Genis-Laval, France), Lutz Wisotzki (Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links:

Research paper: http://www.eso.org/public/archives/releases/sciencepapers/eso1638/eso1638a.pdf

Photos of the VLT: http://www.eso.org/public/images/archive/category/paranal/

Swiss Federal Institute of Technology (ETH): https://www.ethz.ch/en.html

MUSE: https://www.eso.org/public/teles-instr/vlt/vlt-instr/muse/

Very Large Telescope (VLT): http://eso.org/vlt

Image, Videos, Text, Credits: ESO/S. Cantalupo/Borisova et al.

Greetings, Orbiter.ch

Third Lettuce Crop Begins Growing Aboard Station

NASA - Veggie Mission patch.

Oct. 25, 2016

ISS - International Space Station. Image Credit: NASA

Just as farmers on Earth are planting leafy greens for the fall growing season, astronauts aboard the International Space Station are planting their third on-orbit crop of red romaine lettuce.

Early this morning, NASA astronaut Shane Kimbrough initiated the Veg-03 experiment, one of his first science assignments as a new crew member aboard the orbiting laboratory. As Kimbrough worked, members of the Veggie team watched from their consoles in the Experiment Monitoring Area located in Space Station Processing Facility at NASA's Kennedy Space Center in Florida. A live video downlink from the orbiting laboratory allowed the scientists to remotely watch Kimbrough’s actions and ensure he did not encounter any challenges with the activity or hardware.

“Operations went great today! A little slower than expected, but all plant pillows were successfully primed for the first time in our Veg series,” said Nicole Dufour, NASA’s Veggie project manager. Plant pillows are small pouches already containing a growth medium, fertilizer and seeds; to start them growing, astronauts simply add a little water.

“We previously have had some hardware issues that prevented at least one pillow from each ‘grow out’ from being successfully primed, so we were very excited to achieve that milestone,” she added.

Image above: Veggie team members in monitor Veg-03 activation aboard the International Space Station via a live video downlink to the Experiment Monitoring Area located in Space Station Processing Facility at NASA's Kennedy Space Center in Florida. Image Credit: NASA.

Astronauts on future long-duration space missions will need to be able to grow their own food to supplement their diets. Using the Veggie plant growth facility aboard the station, Veg-03 builds on the successes of previous studies, including Veg-01, which resulted in the first-ever on-orbit harvest and sampling of fresh produce during the summer of 2015. Techniques learned from Veggie crops will sow benefits on Earth and help NASA prepare for the Journey to Mars.

The Veg-03 crop will be the Veggie team’s first on-orbit attempt at a new, repetitive harvest technique termed ‘Cut-and-Come-Again’.

“Once the plants are approximately four weeks old, a selection of leaves can be harvested for a bit of fresh lettuce and possibly science samples. Meanwhile, some leaves are left intact along with the core of the plant, and will continue to grow and produce more leaves,” Dufour explained.

 Veggie Will Expand Fresh Food Production on Space Station. Image Credit: NASA

“We expect this will increase the on-orbit crop yield, as well as allow for more opportunities to supplement our astronauts’ diets with fresh, nutritious food from the same plants, which is an important goal of the ‘pick-and-eat’ food concept.”

Dufour reports the team is anxiously awaiting germination results, expected early next week.

Learn more about Veggie and Veg-03:

http://go.nasa.gov/2eKnPro

http://go.nasa.gov/1VCrcnc

Journey to Mars: http://www.nasa.gov/journeytomars

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html

Kennedy Space Center: https://www.nasa.gov/centers/kennedy/home/index.html

Images (mentioned), Text, Credits: NASA's Kennedy Space Center, by Anna Heiney.

Best regards, Orbiter.ch

Feeling the Rhythm

ISS - International Space Station logo.

Oct. 25, 2016

Many astronauts play instruments, and some have even made music in space. Few have danced in space, though, perhaps because crew members find it difficult to tap their toes when weightless. Or it could be that spending time in space throws off their rhythm – at least their circadian rhythm.

Our circadian rhythm, also called the body’s biological clock, coordinates daily variation of physiological functions such as sleep and alertness. Maintaining a circadian rhythm that is synchronized to our 24-hour day is important to health and well-being.

Image above: ESA Astronaut Alexander Gerst wearing a sensor for the experiment on Circadian Rhythms. Image Credit: NASA.

The Circadian Rhythms investigation examines whether long-term spaceflight throws off circadian rhythm in astronauts and the role of factors such as irregular light and dark cycles, microgravity induced changes in body composition, and reduced physical activity.

The body’s core temperature fluctuates during the day in accordance with its circadian rhythm and measuring those changes can show when a person’s body clock is out of whack. Investigators are using a noninvasive sensor placed on the forehead to track core body temperature of several different astronauts before flight, several times during their mission, and post-flight.

“If core body temperatures are altered in flight, this would indicate a de-synchronization of circadian rhythm,” said principal investigator Hanns-Christian Gunga of Universitätsmedizin Berlin in Germany. This research aboard the International Space Station is sponsored by the European Space Agency.

Researchers will correlate the temperature data with pre- and post-flight measures of melatonin, a hormone whose levels follow the classic circadian pattern.

“We want to investigate what happens with the circadian rhythm of body core temperature while orbiting the Earth 16 times a day,” said co-investigator Oliver Opatz. “What might be the impact on other physiological functions such as sleep and the immune system, for example? That would have significance for longer space travel, when this could cause illness.”

Image above: Thermolab control unit and sensors that are placed on the body. Image Credit: ESA.

This work and other studies on circadian rhythms, such as the Lighting Effects investigation, could help crews on future missions better adjust sleep, work, and physical activity to match their natural cycles, improving their productivity and health. Comparing results to the Mars500 sequestering experiment also could contribute to better design of future missions.

Understanding how circadian rhythms change in microgravity also has applications on Earth. It could, for example, help those with sleep, autonomic nervous system, and shift work-related disorders.

In addition, the sensor device has potential uses on Earth as a noninvasive way to measure body temperature in clinical settings.

“Measuring temperature with a device on the surface of the skin is much simpler than other methods. It doesn’t require specialized medical staff to take that measurement, and the patient accepts it readily as well,” said Opatz.

By helping astronauts keep their daily clocks in sync, this investigation could have them dancing through their missions.

Related links:

Music in space: https://science.nasa.gov/science-news/science-at-nasa/2003/04sep_music/

Circadian Rhythms investigation: http://www.nasa.gov/mission_pages/station/research/experiments/892.html

Lighting Effects investigation: http://www.nasa.gov/mission_pages/station/research/experiments/2279.html

Mars500: http://www.esa.int/Our_Activities/Human_Spaceflight/Mars500/Mars500_study_overview

International Space Station (ISS): http://www.nasa.gov/mission_pages/station/main/index.html

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html

European Space Agency (ESA): http://www.esa.int/ESA

NASA Johnson Space Center: https://www.nasa.gov/centers/johnson/home/index.html

Images (mentioned), Text, Credits: NASA Johnson Space Center/Melissa Gaskill/Kristine Rainey.

Greetings, Orbiter.ch

STEREO: 10 Years of Revolutionary Solar Views

NASA - STEREO Mission logo.

Oct. 25, 2016

Launched 10 years ago, on Oct. 25, 2006, the twin spacecraft of NASA’s STEREO mission – short for Solar and Terrestrial Relations Observatory – have given us unprecedented views of the sun, including the first-ever simultaneous view of the entire star at once. This kind of comprehensive data is key to understanding how the sun erupts with things like coronal mass ejections and energetic particles, as well as how those events move through space, sometimes impacting Earth and other worlds. Ten years ago, the twin STEREO spacecraft joined a fleet of NASA spacecraft monitoring the sun and its influence on Earth and space – and they provided a new and unique perspective.

STEREO Mission Turns 10

Video Credits: NASA's Goddard Space Flight Center/Genna Duberstein, producer.

The two STEREO observatories, called STEREO-A and STEREO-B – for Ahead and Behind, respectively – were sent out from Earth in opposite directions. Using gravitational assists from both the moon and Earth, the STEREO spacecraft were accelerated to Earth-escape velocities. STEREO-A was inserted into an orbit slightly smaller, and therefore faster, than Earth’s. For STEREO-B, the reverse happened: It was nudged into an orbit slightly larger than Earth’s so that it traveled around the sun more slowly, falling increasingly behind the Earth. As the spacecraft slowly fanned out away from the centerline between Earth and the sun – where every other sun-watching spacecraft is located – they revealed more and more new information about our closest star.

“STEREO gives us a much more thorough view of the sun, solar wind and solar activity,” said Terry Kucera, deputy project scientist for STEREO at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The view from the far side of the sun lets us record more events and get more complete pictures of each event.”

When observed through a solar telescope, the surface of the sun can be seen to be churning with near-constant activity, sometimes including the larger solar eruptions that can influence Earth, other worlds, and space itself. We call these changing conditions space weather. On Earth, space weather often manifests as auroras, or – in extreme cases – damage to satellites or stress on power grids.

Animation above: This composite view shows the sun as it appeared on Jan. 31, 2011, with simultaneous views from both of NASA’s STEREO spacecraft and NASA’s Solar Dynamics Observatory. These three distinct viewpoints allowed scientists to capture almost the entire sun at once, with only a small gap in data. Animation Credits: NASA/Goddard/STEREO.

The prime STEREO mission was designed for two years of operations, observing the sun and the space environment around it, by which point the spacecraft would have traveled about 45 degrees (one-eighth of a circle each) away from Earth. This mission design was revolutionary, since our observations of the sun and conditions in space had previously been confined to views only from Earth's perspective. By providing us with different views of the sun simultaneously, STEREO helped scientists watch solar eruptions develop over time, and gave them multiple perspectives of how those eruptions propagate outward. The greater the separation of the two spacecraft from each other and from Earth, the more we learned about the sun and its influence on space – including multi-point views of one of the most powerful solar storms on record.

“STEREO had unique perspectives of a powerful CME on July 2012, which was strong enough to cause serious disruptions if it had been Earth-directed,” said Joe Gurman, STEREO project scientist at Goddard. “We got a head-on look with STEREO-A, a side view with STEREO-B as well as observations by Earth-orbiting satellites.”

However, STEREO’s real windfall is the sheer amount of data collected. Both spacecraft functioned well for nearly eight years, yielding a treasure trove of data on solar events.

“Real science doesn’t come from just one event,” said Gurman. “The biggest advantage of STEREO is being able to validate our models of how CMEs move through space.”

Animation above: This animation shows the orbits of the two STEREO spacecraft from October 2006 to October 2016. Because of the twin probes’ unique positions in space, the STEREO mission has given scientists an unprecedented look at the sun, helping us to understand our home star. Animation Credits: NASA Goddard's Scientific Visualization Studio.

STEREO-A continues to collect data. However, STEREO-B encountered an issue when the spacecraft approached a phase called superior conjunction – when the sun would stand between the spacecraft and Earth, blocking all communications. During testing in October 2014 to prepare for superior conjunction, contact with STEREO-B was lost. After nearly two years, on Aug. 21, 2016, mission operators managed to contact STEREO-B once again, and have been in touch intermittently since then. This contact has revealed new information about the spacecraft’s battery and charge state, its position in space, its speed and its spin – and mission operators continue to attempt recovery.

“The challenges for a successful recovery are many,” said Dan Ossing, the STEREO mission operations manager at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. “It’s an incremental process that continues to evolve, and could take months or even years. But we know enough of the spacecraft has survived to make these recovery attempts worthwhile. We just have to be patient.”

Though STEREO-A was silent for nearly four months because of superior conjunction, after contact was re-established it returned the data recorded on the sun’s far side, filling in this gap in the timeline of solar data. The STEREO-A spacecraft is now operating fully, maintaining this stream of information.

“It’s these long term measurements that are critical for understanding the sun,” said Gurman.

STEREO is the third mission in NASA's Solar Terrestrial Probes program, which is managed by NASA Goddard for NASA’s Science Mission Directorate in Washington. It was built by the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.

Related Link

NASA’s STEREO website: https://www.nasa.gov/mission_pages/stereo/main/index.html

Animations (mentioned), Video (mentioned), Text, Credits: NASA's Goddard Space Flight Center, by Sarah Frazier/Rob Garner.

Greetings, Orbiter.ch