‘Not All Hope Is Lost’: NASA Sun Probe Silent Now For Six Weeks

No one knows exactly why a NASA solar probe stopped talking to Earth six weeks ago, but it’s possible the spacecraft is out of power and is drifting without a way of calling for help, the agency said in an update.

On Oct. 1, NASA suddenly lost contact with one of the two Solar TErrestrial RElations Observatory (STEREO) spacecraft, which are currently examining the far side of the Sun. The probes are considered crucial for solar forecasting, so the loss is a blow. While the STEREO-Behind probe has been mute since then, the agency says “not all hope is lost” for a recovery.

STEREO-Behind went silent after NASA deliberately reset the spacecraft. Along with its twin, STEREO-Ahead, in the coming years the spacecraft will need to reposition its antenna to avoid getting fried by the Sun. Also, there is a period where each spacecraft will need to work autonomously, because the Sun’s radio interference will make it difficult or impossible for communications to get through.

First complete image of the far side of the sun taken on June 1, 2011. Click image for larger version. Credit: NASA/STEREO.
First complete image of the far side of the sun taken on June 1, 2011. Click image for larger version. Credit: NASA/STEREO.

To prepare the spacecraft, NASA has been testing them out ahead of these events, which are called “solar conjunction operations.” STEREO-Ahead passed the tests and entered these operations in August, where it will remain until 2016. STEREO-Behind was supposed to go into this phase on Dec. 1. Preparations started Sept. 27, when STEREO-Behind was put into the same safe mode test that was used on STEREO-Ahead.

“One part of this test was to observe the firing of the spacecraft hard command loss timer, which resets the spacecraft if no commands are received after three days,” NASA wrote in an update. “The purpose of this is to correct any problems that might be preventing the spacecraft from receiving commands from the ground. While the spacecraft is out of contact on the far side of the Sun, this reset will occur every three days.”

The timer did fire as planned on Oct. 1, and the spacecraft reset as expected. However, the radio signal coming from STEREO-Behind wasn’t as strong as expected. Then, it disappeared altogether.

An artist's concept shows both STEREO surrounding the sun on opposite sides. Credit: NASA
An artist’s concept shows both STEREO surrounding the sun on opposite sides. Credit: NASA

While there’s not much information to work with, NASA says it does know a few things. Before the reset, information or telemetry from the spacecraft showed it was working fine. After the reset, though, they could tell the inertial measurement unit (IMU) was turned on. This is unusual, and shows that the guidance system’s star tracker hadn’t picked up its guide stars as expected.

“This is not unexpected—there have been other occasions when it took the star tracker several minutes, or even a few days, to start determining the spacecraft orientation based on star images,” NASA said.

“In fact, on Sept. 28, as part of the same test sequence, the spacecraft was reset, and it took 12 minutes for the star tracker to start providing an attitude solution. When the star tracker is ofline, the spacecraft will automatically turn on the IMU to provide rotational rate information.”

Deployment of STEREO Spacecraft Panels. Credit: 2002-Johns Hopkins University Applied Physics Laboratory. Credit: Dr C.J.Eyles, University of Birmingham
Deployment of STEREO Spacecraft Panels. Credit: 2002-Johns Hopkins University Applied Physics Laboratory. Credit: Dr C.J.Eyles, University of Birmingham

NASA thinks the star tracker’s struggles would explain why the radio signal wasn’t as strong as expected, because the spacecraft’s high-gain antenna wasn’t aimed at Earth properly. But there’s more — it appears one of the IMU’s laser gyroscopes isn’t working and is giving “bad data to the attitude control system”, NASA said. So now the spacecraft was facing two failures, which is tough for it to deal with, the agency added.

Did the spacecraft recognize the problem? If it did, it would have used the last backup system — five solar aspect sensors — which should have made sure the solar panels were pointed in the right direction to provide power. If not, the spacecraft might have thought it was in a roll, turned on its thrusters, and then spun itself in such a way that it could have lost sunlight power.

NASA is trying to send out commands to address all of these failure possibilities, and it emphasizes that a recovery is still possible. The Solar and Heliospheric Observatory (SOHO), for example, also lost power in 1998 when a spin put its solar panels out of reach of the Sun. However, as its orbit changed, the Sun’s light eventually fell across the panels and power was restored. The spacecraft was recovered and still works today.

Source: NASA

NASA Solar Forecasting Takes A Hit As Sun-Gazing Spacecraft Stops Phoning Home

A NASA spacecraft has been out of radio contact for about two weeks, but the agency is still holding out hopes for a rescue. One of the STEREO (Solar TErrestrial RElations Observatory) spacecraft stopped phoning home to Earth on Oct. 1 “immediately after a planned reset of the spacecraft”, NASA said in an update last week.

If the STEREO-Behind spacecraft can’t be recovered, this could cause a data gap in the mission next year — which is unique because it looks at the far side of the Sun. On the website, NASA didn’t say how badly solar weather forecasts are affected, but in other materials they have said both STEREO spacecraft are a crucial part of this work.

STEREO’s pair of satellites (STEREO-Ahead and STEREO-Behind) aim to better map Sun eruptions (known as “coronal mass ejections”) whose charged particles can disrupt satellite communications during solar storms. The mission has been ongoing since 2006 and they’ve viewed the far side of the Sun since 2011. What caused one of them to stop talking to us is unknown, but NASA said recovery attempts are ongoing.

The satellites’ orbits around the Sun are similar to the Earth’s, but one circles a bit faster and the other a bit slower. Next year, geometry (a solar conjunction) means the Sun will block our view of one of the spacecraft at a time. As NASA explained in a July update, “radio receivers on Earth will not be able to distinguish STEREO’s signal from the sun’s radiation.”

This is affecting the mission in two ways. First, there is a period where the antennas on the spacecraft must be repositioned to avoid getting cooked by the Sun. Some data will flow, but it will be in lower resolution. STEREO-Ahead entered this period on Aug. 20, and STEREO-Behind was supposed to send high-resolution data until Dec. 1.

Then there’s a time when each spacecraft will be completely blocked by the Sun. STEREO-Behind was supposed to enter this period from Jan. 22 to March 23, 2015, with its twin still collecting data at this time. But then will come a period where STEREO-Ahead will be out of contact: March 24 to July 7, 2015. If STEREO-Behind can’t fill in for STEREO-Ahead at this time as planned, a data gap could loom.

Lower-resolution data is then expected from STEREO until 2016, when the geometry means the spacecraft can safely reposition their antennas. While these aren’t the only sun-gazing spacecraft — real-time data is still flowing from the Solar Dynamics Observatory (SDO) and the Solar and Heliospheric Observatory (SOHO) — NASA has said that the lower data rate and losing contact with one STEREO spacecraft next year will be difficult for solar forecasting.

“Lack of STEREO observations used in NASA research models will severely limit the forecasting of solar storms throughout the solar system,” the agency said in a July Q&A about the 2015 data losses.

NASA’s STEREO Spacecraft Spots Comets ISON and Encke

As comets ISON and Encke continue toward their respective rendezvous with the Sun, they have now both been captured on camera by NASA’s solar-observing STEREO spacecraft. The image above, taken on Nov. 21 (UT) with STEREO-A’s high-resolution HI-1 camera, shows ISON as it enters the field of view from the left. Encke is at center, while the planets Mercury and Earth (labeled) are bright enough to cause vertical disruptions in the imaging sensors. (The Sun is off frame to the right.)

As cool as this image is, it gets even better: there’s a video version. Check it out below:

Animation of STEREO-A images acquired on Nov. 20-21 (Karl Battams/NASA/STEREO/CIOC)
Animation of STEREO-A images acquired on Nov. 20-21 (Karl Battams/NASA/STEREO/CIOC)

The dark “clouds” coming from the right are density enhancements in the solar wind, causing all the ripples in comet Encke’s tail. (Source)

The position of NASA's STEREO spacecraft relative to Earth and the Sun on Nov. 22
The position of NASA’s STEREO spacecraft relative to Earth and the Sun on Nov. 22

It’s fascinating to watch how the solar wind shapes and affects the tail of comet Encke… as ISON moves further into view, I’m sure we’ll see similar disruptions in its tail as well. (And look what STEREO-A saw happen to Encke’s tail back in 2007!)

Encke reached the perihelion of its 3.3-year-long orbit on Nov. 21; newcomer ISON will arrive at its on Nov. 28. While it seems to be holding together quite well in these STEREO images, what happens when it comes within 730,000 miles of the Sun next week is still anybody’s guess.

Read more: Whoa, Take a Look at Comet ISON Now!

Asteroid Vs. Comet: What The Heck Is 3200 Phaethon?

Sometimes, putting things into categories difficult. Witness how many members of the general public are still unhappy that Pluto was reclassified as a dwarf planet, a decision made by the International Astronomical Union more than seven years ago.

And now we have 3200 Phaethon, an asteroid that is actually behaving like a comet. Scientists found dust that is streaming from this space rock as it gets close to the sun — similarly to how ices melt and form a tail as comets zoom by our closest stellar neighbor.

Phaethon’s orbit puts it in the same originating region as other asteroids (between Mars and Jupiter), but its dust stream is much closer to actions performed by a comet — an object that typically comes from an icy region way beyond Neptune. So far, therefore, the research team is calling Phaethon a “rock comet.” And after first proposing a theory a few years ago, they now have observations as to what may be going on.

Phaethon is not only an asteroid, but also a source of a prominent meteor shower called the Geminids. This shower happens every year around December when the Earth plows into the cloud of debris that Phaethon leaves in its wake. Astronomers have known about the Geminids’ source for a generation, but for decades could not catch the asteroid in the act of shedding its stuff.

That finally came with images of NASA’s twin sun-gazing Solar TErrestrial RElations Observatory (STEREO) spacecraft that were taken between 2009 and 2012. The researchers saw a “comet-like tail” extending from the 3.1-mile (five kilometer) asteroid. “The tail gives incontrovertible evidence that Phaethon ejects dust,” stated David Jewitt, an astronomer at the University of California, Los Angeles who led the research. “That still leaves the question: why?”

Time lapse-photo showing geminids over Pendleton, OR. Credit: Thomas W. Earle
Time lapse-photo showing geminids over Pendleton, OR. Credit: Thomas W. Earle

The answer lies in just how close Phaethon whizzes past the sun. At perihelion, its closest approach to the sun, it only appears eight degrees (16 solar diameters) away from the sun in Earth’s sky. This close distance makes it all but impossible to study the asteroid without special equipment, which is why STEREO came in so handy.

When Phaethon reaches its closest approach of 0.14 Earth-sun distances, surface temperatures rise above an estimated 1,300 degrees Fahrenheit (700 degrees Celsius). It’ s way too hot for ice, as what happens with a comet. In fact, it’s probably hot enough to make the rocks crack and break apart. The researchers publicly hypothesized this was happening at least as far back as 2010, but this finding provided more evidence to support that theory.

“The team believes that thermal fracture and desiccation fracture (formed like mud cracks in a dry lake bed) may be launching small dust particles that are then picked up by sunlight and pushed into the tail,” a statement from the research team read.

“While this is the first time that thermal disintegration has been found to play an important role in the solar system,” they added, “astronomers have already detected unexpected amounts of hot dust around some nearby stars that might have been similarly produced.”

The results were presented at the European Planetary Science Congress on Tuesday. By the way, STEREO also caught Mercury behaving somewhat like a comet in results released in 2010, although that find was related to the planet’s escaping sodium atmosphere.

Read more about the research in the June 26 issue of Astrophysical Letters. A preprint version is also available on Arxiv.

Source: European Planetary Science Congress

STEREO Spots a CME Soaring Into Space

Press “play.” Say “wow.”

The enormous eruption of a solar prominence and resulting coronal mass ejection (CME) back on August 31 that was captured in amazing HD by NASA’s Solar Dynamics Observatory was also spotted by the Sun-flanking STEREO-B spacecraft, which observed the gigantic gout of solar material soaring away from the Sun.

This video shows the eruption as it passes across the fields of view of several of STEREO-B’s cameras over the course of 48 hours.

According to NASA’s Goddard Space Flight Center, “while CMEs are routinely seen in the Heliographic Imager (HI) telescopes, it’s very rare for prominences to stay visible for so long. The HI1 field of view ranges from 4 to 24 degrees away from the Sun. To get a sense of scale, we know the Sun is roughly 860,000 miles wide — and look how far the prominence holds together. And this CME is so bright it initially saturates the COR1 telescope.”

The bright spot in the red (COR2) field of view is the planet Venus.

Coronal mass ejections are huge bubbles of gas bounded by magnetic field lines that are ejected from the Sun over the course of several minutes — sometimes even hours. If they are directed toward Earth, the cloud of charged solar particles can interact with our magnetosphere and cause anything from increased auroral activity to radio interference to failure of sensitive electromagnetic equipment.

Particularly long filaments like the one that caused the August 31 CME have been known to collapse with explosive results when they hit the stellar surface.

The CME did not travel directly toward Earth but did connect with Earth’s magnetosphere with a glancing blow, causing bright aurorae to appear around the upper latitudes on the night of September 3.

Image: NASA/STEREO/GSFC

NASA’s STEREO Spots a New Nova


While on duty observing the Sun from its position in solar orbit, NASA’s STEREO-B spacecraft captured the sudden appearance of a distant bright object. This flare-up turned out to be a nova — designated Sagittarii 2012 — the violent expulsion of material and radiation from a re-igniting white dwarf star.

Unlike a supernova, which is the cataclysmic collapse and explosion of a massive star whose core has finally fused its last, a nova is the result of material falling onto the surface of a white dwarf that’s part of a binary pair. The material, typically hydrogen and helium gas, is drawn off the white dwarf’s partner which has expanded into a red giant.

Eventually the white dwarf cannot contain all of the material that it has sucked in from its neighbor… material which has been heated to tremendous temperatures on its surface as it got compressed further and further by the white dwarf’s incredibly strong gravity. Fusion occurs on the dwarf’s outermost layers, blasting its surface out into space in an explosion of light and energy.

This is a nova — so called because, when witnessed in the night sky, one could suddenly appear as a “new star” in the heavens — sometimes even outshining all other visible stars!

An individual nova will soon fade, but a white dwarf can produce many such flares over time. It all depends on how rapidly it’s accreting material (and how much there is available.)

Over the course of 4 days, Sagittarii 2012 reached a magnitude of about 8.5… still too dim to be seen with the unaided eye, but STEREO-B was able to detect it with its SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation) instrument, which is sensitive to extreme ultraviolet wavelengths.

The video above was made from images acquired from April 20 – 24, 2012.

It’s not known yet how far away Sagittarii 2012 is but rest assured it poses no threat to Earth. The energy expelled by a nova is nowhere near that of a supernova, and although you wouldn’t want to have a front-row seat to such an event we’re well away from the danger zone.

What this does show is that STEREO-B is not only a super Sun-watching sentinel, but also very good at observing much more distant stars as well!

Thanks to @SungrazerComets for the heads-up on this novel nova!

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Watch Mercury Get Smacked By CMEs

mercuryandsun.thumbnail.jpg

The bright object in the center of this video sequence is the planet Mercury, seen by NASA’s STEREO-B spacecraft as it was pummeled by wave after wave of solar material ejected from the Sun during the week of March 25 – April 2, 2012.

The video above was released by NASA’s Goddard Space Flight Center earlier today. The Sun is located just off-frame to the left, while Earth would be millions of miles to the right.

Proof that it’s not easy being first rock from the Sun!

Video credit: NASA/GSFC/STEREO

Navy Scientists Spot New Solar Structures

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There’s something new under the Sun… well, just above the Sun, actually. Scientists at the Naval Research Laboratory have spotted structures in the Sun’s super-hot corona that may shed some light on the way its magnetic fields evolve — especially near the edges of vast, wind-spewing coronal holes.

Coronal holes are regions where the Sun’s magnetic field doesn’t loop back down but rather streams outward into space. Appearing dark in images captured in ultraviolet wavelengths, these holes in the corona allow solar material to flow directly out into the solar system, in many cases doubling the normal rate of the solar wind.

Recently witnessed by NRL researchers using NASA’s SDO and STEREO solar-observing spacecraft, features called coronal cells exist at the boundaries of coronal holes and may be closely associated with their formation and behavior.

The coronal cells are plumes of magnetic activity that stream upward from the Sun, occurring in clusters. Likened to “candles on a birthday cake”, the incredibly hot (1 million K) plumes extend outwards, punching though the lower corona.

Seen near the center of the Sun’s disk, the cells appear structurally similar to granules — short-lived areas of rising and falling solar material on the Sun’s photosphere — but seen from an angle via STEREO, the cells were witnessed to be much larger, elongated and extending higher into the Sun’s atmosphere. For comparison, granules are typically about 1,000 km in diameter while the coronal cells have been measured at 30,000 km across.

“We think the coronal cells look like flames shooting up, like candles on a birthday cake,” said Neil Sheeley, a solar scientist at the Naval Research Laboratory in Washington, D.C. “When you see them from the side, they look like flames. When you look at them straight down they look like cells. And we had a great way of checking this out, because we could look at them from the top and from the side at the same time using observations from SDO, STEREO-A, and STEREO-B.”

Watch a video below of cells made from images acquired by STEREO-B… note how their elongated structure becomes evident as the cells rotate closer to the Sun’s limb.

NRL researchers also noted that the coronal cells appeared when adjacent coronal holes closed and disappeared when the holes opened, suggesting that the holes and cells share the same magnetic structure. In addition, the coronal cells were seen to disappear when a solar filament would erupt nearby, being “extinguished” as the cooler strand of solar material moved across them. Once the filament passed, the cells reformed — again, indicating a direct magnetic association.

The coronal cells were also identified in earlier images from ESA and NASA’s SOHO and Japan’s Hinode spacecraft.

It’s hoped that further study of these candle-like structures will lead to more knowledge of our star’s complex magnetic field and the effects it has on space weather and geomagnetic activity experienced here on Earth.

Read the press release from the Naval Research Laboratory here, and on NASA’s STEREO site here.

I Thought I Saw A UFO! Mystery Triangle On STEREO Image Explained…

Mystery diamond-shape “object” entering the field-of-view of the HI2 telescope on STEREO Behind around December 26, 2011. Credit: NASA

The STEREO (Solar TErrestrial RElations Observatory) is a two-year mission conducted by NASA. It employs nearly identical twin telescopes – one positioned ahead of Earth’s orbit and the other behind – designed to study the Sun’s activities spectroscopically. However, it can sometimes pick up some very unusual findings! On December 26, 2011, the STEREO Behind Observatory’s HI2 telescope captured an ambiguous triangle entering the field of view and moving from right to left just above the trapezoidal occulter as seen in the above movie. Just what is this “thing”?!

Before you get ready to call the men in black, know that there is a logical answer… and it comes into play on the opposite side of the STEREO image. Play the movie again and watch. (It’s a bit more obvious in this close-up view.) Just as the weird triangle begins its approach, you’ll notice the dazzling Venus enters the field of view of the HI2-B at the same time to the lower left. As you watch, you’ll see they keep exactly the same time – in opposite – across the detector image. This isn’t just a chance happening… it’s a naturally-occurring internal reflection caused by Venus’ brilliance in the telescope’s optics. It might be exciting for the moment, but it’s nothing that hasn’t happened in the past. Just check out these great STEREO Reflections of Earth, and all sorts of other cool images on the STEREO Image Artifacts pages.

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What else can be seen? As you can tell from this photograph, Earth is also starring in the show, but doesn’t come in as striking as Venus. What’s more you can also see the tail of Comet Lovejoy streaking in from the left just above Venus towards the end of the movie.

Exactly how do you keep track of what’s going on? Check out the Where Is STEREO? pages for up-to-date information and the totally cool Current STEREO Solar Images!

Original Story Source: Triangular shaped object in STEREO data explained.

Watch as Comet Lovejoy Takes a Death-Dive Into the Sun

A comet discovered on Dec. 2, 2011 is now on a near collision course with the Sun, and likely won’t survive such a close encounter. The best part is that you can follow along and watch as it happens! Comet C/2011 W3 Lovejoy will pass behind the sun at around 24:00 UTC (7 pm EST) on Thursday, Dec. 15, 2011 and probably won’t be seen again. In the video above, processed images from the STEREO A spacecraft shows Comet Lovejoy blazing towards the Sun, with the comet’s tail wiggling as it interacts with the solar wind.

The Solar Dynamics Observatory website has a special page where they will be uploading the latest images of the comet as it meets its fiery fate. As Comet Lovejoy moves toward perihelion, the SDO team will point SDO a little to the left of the Sun to try and see the tail of the comet with their instruments. This website will allow you to see those images as quickly as they can download them from the spacecraft.

Science live and in action!

Astronomers and various spacecraft have been keeping an eye on Comet Lovejoy the past few days as this Kreutz-group comet headed towards the Sun. Just today (Thursday) the images from the SOHO spacecraft showed the comet sprouting a bulbous head. This is occurring because the comet is getting so bright, it is overwhelming the detectors on the SOHO satellite. “The photons are ‘bleeding’ out to form that cross-like pattern,” said Dan Pendick on the Geeked On Goddard website.

Pendick also quoted solar scientist Jack Ireland from Goddard, who noted that at times two tails can be seen on the comet. “The thick white tail is primarily dust breaking away from the comet nucleus,” Ireland said, as the Sun’s radiation and solar wind that knocks material off the comet nucleus. But to the left is a tail of charged particles (ions) being deflected to the side by the magnetic field carried by the solar wind.

At its closest approach, Comet Lovejoy will pass just 120,000 km above the solar surface. At that distance, the icy comet is not expected to survive the Sun’s fierce heat. But the comet could actually disintegrate at any moment. Kreutz comets have a tendency to evaporate as they approach, or pass close to the Sun.

If the comet does stay the course and stay visible until it goes around the Sun, we likely won’t be able to see its demise because its closest approach will take place on the far side of the Sun.

But this is a great chance to watch this event as it is about to happen.

“We have here an exceptionally rare opportunity to observe the complete vaporization of a relatively large comet, and we have approximately 18 instruments on five different satellites that are trying to do just that,” wrote Karl Battams, from the Naval Research Laboratory, who curates the Sun-grazing comets webpage, and has been documenting Lovejoy’s journey.

Amateur astronomers have been trying to capture this event as well, with everyone wondering how bright the comet will get. For updates from amateur astronomers, check out the Yahoo Groups comet observers forum.

Comet C/2011 W3 Lovejoy was actually discovered by an amateur, Australian astronomer Terry Lovejoy (hence the comet’s name.) This is the first Kreutz comet found from a ground-based observer since 1970, and it was spotted with a modest 8″ telescope too! You can read Lovejoy’s tale of his discovery here.

On average, new Kreutz-group comets are discovered every few days by spacecraft like SOHO, but from the ground they are much rarer to see and harder to discover.

“This is the first ground-based discovery of a Kreutz-group comet in 40 years, so we really can’t be sure just how bright it will get,” said Battams. “However, I do think that it will be the brightest Kreutz-group comet SOHO has ever seen.”

Comet Lovejoy’s spectacular progress can also be monitored via the web at SOHO’s LASCO instrument page.

For the SDO special webpage, images from SDO take about 30 minutes to move from the spacecraft until they are available on the website. The SOD team plans to off-point the spacecraft at 23:30 UTC (6:30 pm ET) and return to normal solar observing at 12/16 00:30 UTC (7:30 pm ET). Images should start arriving by 24:00 UTC (7 pm EST.)