8.09.2023
Camera ‘hack’ lets Solar Orbiter peer deeper into Sun’s atmosphere
Scientists have used Solar Orbiter’s EUI camera in a new mode of operation to record part of the Sun’s atmosphere at extreme ultraviolet wavelengths that has been almost impossible to image until now. This new mode of operation was made possible with a last-minute ‘hack’ to the camera and will almost certainly influence new solar instruments for future missions.
Solar Orbiter’s Extreme Ultraviolet Imager (EUI) returns high-resolution images of the structures in the Sun’s atmosphere. Scientists call this region the corona. During EUI’s construction, a last-minute modification to the safety door on the front of the instrument has allowed it to see deeper into its target region than originally specified.
“It was really a hack,” says Frédéric Auchère, Institut d'Astrophysique Spatiale, Université Paris-Sud, and a member of the EUI team. “I had the idea to just do it and see if it would work. It is actually a very simple modification to the instrument.”
It involved adding a small, protruding ‘thumb’, weighing a few grams, to the door of the instrument. As the door slides out of the way to let the light into the camera, if it is stopped halfway, the thumb covers the Sun’s bright disc, and EUI can detect the million-times fainter ultraviolet light coming from the surrounding corona.
The team refer to this as the occulter mode of operation. Tests with the EUI occulter have been on-going since 2021. Now the team are confident in its successful operation and have written a paper and published a video showing the results.
Access the video
The movie shows an ultraviolet image of the Sun’s corona taken using the EUI occulter. An ultraviolet image of the Sun’s disc has been superimposed in the middle, in the area left blank by the occulter. The image of the Sun’s disc has been taken by NASA’s STEREO mission, which happened to be looking at the Sun from almost the same direction as Solar Orbiter at the same time, so the features on the surface have a good correlation to the features in the corona.
In the past, images of the Sun’s corona have been taken with dedicated instruments called coronagraphs. For example, Solar Orbiter’s coronagraph is called Metis. The value of this new approach is that the coronagraph and the camera can be included in the same instrument.
“We’ve shown that this works so well that you can now consider a new type of instrument that can do both imaging of the Sun and the corona around it,” says Daniel Müller, ESA’s Project Scientist for Solar Orbiter.
Even before those new instruments, there is a lot of new science to come from EUI. The occulter mode makes it possible for scientists to see deeper into the Sun’s atmosphere. This is the region that lies beyond the field of view of classical EUV imagers but it is usually obscured by traditional coronagraphs. Now, however, EUI’s occulter can image this little-explored region easily.
“Physics is changing there, the magnetic structures are changing there, and we never really had a good look at it before. There must be some secrets in there that we can now find,” says David Berghmans, Royal Observatory of Belgium, and the EUI Principal Investigator.
Solar Orbiter is a space mission of international collaboration between ESA and NASA, operated by ESA.
Quelle: ESA
----
'Lightning' on Venus may not be lightning at all, Parker Solar Probe finds
While studying the sun, Parker might have also solved a longstanding Venusian puzzle.
An artist's depiction of NASA's Parker Solar Probe flying past Venus. (Image credit: NASA/Johns Hopkins APL/Steve Gribben)
While zipping through space on its seven-year-long mission to investigate the sun, NASA's Parker Solar Probe may have finally picked up signals of the culprit behind Venus' mysterious "lightning" storms. The find happened in 2021, when Parker made a routine flyby of the windy world in an effort to harness the planet's gravitational pull and propel itself closer to its primary stellar subject.
"Parker Solar Probe is a very capable spacecraft. Everywhere it goes, it finds something new," Harriet George, lead author of the new study and a postdoctoral researcher at the Laboratory for Atmospheric and Space Physics, said in a statement.
In a nutshell, per a new paper on the 2021 Parker data, flashes of light on Venusthat many experts associate with lightning bolts might not represent lightning bolts at all. Rather, they appear connected to disturbances in the magnetic fields surrounding the planet. Of course, that's not to say Venus doesn't have some lightning — perhaps just not as much as we once thought.
"There's been debate about lightning on Venus for close to 40 years," George said. "Hopefully, with our newly available data, we can help to reconcile that debate."
Essentially, though Venus seems riddled with lightning bolts based on signals scientists have collected over time, something doesn't quite add up. For instance, a 2021 study, the statement says, failed to find the radio waves you'd expect to see from lightning on the planet — and a paper published in August of this year suggests some flashes of light typically attributed to Venusian bolts are actually meteors burning up in the planet's atmosphere.
Listen to the whistler waves
Basically, the way George and fellow researchers drew their conclusions about Venus' lightning — or lack thereof — is by tracing a phenomenon known as "whistler waves."
Whistler waves are fleeting pulses of energy expressed as electromagnetic waves that can propagate through various mediums; on Earth, for instance, they propagate through part of the atmosphere and generally last about half a second. But most importantly, on Earth, these whistler waves are specifically rooted in lightning discharges.
So, when scientists noticed whistler waves on Venus for the first time in 1978 thanks to the Pioneer Venus spacecraft, it's understandable why they assumed Venus must have lots of lightning. So much, in fact, that many experts believed Venus must experience roughly seven times more lightning than our planet does, according to a statement on the new study.
"Some scientists saw those signatures and said, 'That could be lightning,'" George said. "Others have said, 'Actually, it could be something else.' There’s been back and forth about it for decades since."
After Pioneer's findings, the Galileo spacecraft found further evidence of lightning in 1990, yet Cassini's flybys in 1998 and 1999 failed to find the evidence of radio static on Venus you'd expect to accompany lightning. Then, Venus Express, the first European Venus orbiter, identified some promising proof between 2006 and 2014 that, yes, there is lightning on Earth's "evil twin." It's all very questionable, but the final answer about lightning bolts on Venus could be in sight — especially because Parker's data was collected when the probe was significantly close to the planet. It was only about 1,500 miles (2,414 kilometers) away.
As George explains, whistler waves don't necessarily have to be created by lightning — and when Parker flew by the straw-colored planet a few years ago, it got incredibly close and collected data that indeed suggested Venus' whistler waves do not come from lightning.
The researchers saw those whistler waves heading downward toward the planet, not outward like the direction Earth's lightning-induced whistler waves move to propagate through the atmosphere. "They were heading backward from what everybody had been imagining for the last 40 years," David Malaspina, co-author of the study and an assistant professor at LASP.
From there, the team theorized that the waves stem from disturbances in the planet's magnetic fields. Or, more specifically, the idea is that magnetic field lines surrounding Venus may break apart then snap back together, in turn producing bursts of energy exhibited as none other than whistler waves.
In 2024, Parker will make its seventh and final pass by Venus as it treads closer and closer to the sun. That flyby will bring it less than 250 miles above the Venusian surface.
Hopefully that's enough proximity to settle the planet's lightning debate once and for all.
The paper detailing these findings was published on Sept. 29 in the journal Geophysical Research Letters.
Quelle: SC
----
Update: 18.10.2023
.
Here’s another strike against Venus having copious lightning
Electromagnetic disturbances in its atmosphere were generated by another energy source
Venus has long been depicted as having a hellish atmosphere. Despite that reputation, evidence increasingly suggests that our neighbor’s cloudy shroud isn’t riddled with lightning.
Last month, planetary scientists proposed that most if not all of the bright flashes observed in Venus’ atmosphere could be explained by meteors (SN: 9/11/23). Now, a separate team suggests that whistling electromagnetic waves often created by lightning on Earth and other planets are not sparked by lightning on Venus.
n 2021, the Parker Solar Probe swung past the nighttime side of Venus on its way toward the sun (SN: 12/15/21). As it did, its instruments picked up radio waves that scientists have dubbed whistler waves. Such disturbances got their name because their frequency quickly changes from high to low before they disappear, says Harriet George, a space physicist at the University of Colorado Boulder.
Oddly, Venus’ whistler waves were traveling downward toward the planet, not up and away from it, as they would have been if they’d been caused by lightning, George and her team report in the Oct. 16 Geophysical Research Letters.
An alternate source of energy for these whistler waves could be disturbances in Venus’ weak magnetic fields, the researchers suggest. As magnetic field lines shift and reconnect, they can release prodigious amounts of energy, George says. In other milieus, magnetic reconnections accelerate the solar wind, help heat the sun’s outer atmosphere and help trigger Earth’s auroras. They’ve got the right characteristics to create whistler waves on Venus too.
Quelle: ScienceNews
----
Update: 7.11.2023
.
ESA's Proba-3 Formation Flying Mission Proceeds to Final Checks
The European Space Agency's (ESA) ambitious Proba-3 mission has recently completed a critical environmental testing campaign, marking a significant milestone on its path toward a 2024 launch. Conducted in Ottobrunn, Germany, these tests have proven that the mission's equipment can endure the harsh conditions of launch and the extreme thermal environment of outer space. The comprehensive campaign included activation tests for the mission's mechanisms and a thorough validation of the propulsion system, ensuring readiness for the operational challenges ahead.
Proba-3 represents a pioneering endeavor for ESA, aimed at demonstrating high-precision formation flying between two spacecraft. This technique has profound implications for future space missions, particularly those requiring synchronized operation of separate platforms. The two satellites will maintain close proximity while orbiting Earth, creating an artificial eclipse to study the Sun's obscured corona-a region typically concealed by the sun's bright light.
The complexity of Proba-3 is heightened by the autonomy required of its onboard algorithms, along with the intricate operations and coordination for the two spacecraft, which will navigate through space at a separation as minimal as a few hundred meters.
The mission leverages an international consortium of industry specialists, led by the engineering company Sener, with contributions from over 29 enterprises across 14 nations. This collaborative effort underlines the transnational commitment to advancing space exploration technologies.
Within this consortium, GMV plays a pivotal role, tasked with the formation flying subsystem (FFS), one of the mission's most sophisticated and critical onboard elements. GMV's responsibilities stretch from the design and development to the validation of the FFS's onboard software, simulated within a virtual environment replicating the onboard computer and its electrical interfaces. GMV's remit also extends to supplying the ground segment's flight dynamics system, encompassing the monitoring and control of flight, orbit determination, and prediction of maneuvers.
Collaboration is key in the Proba-3 project, with GMV in Spain partnering with Sener for the control and failure detection systems, Canada's NGC for the attitude and orbit control, and GMV in Poland for the onboard function that computes satellite relative positioning using GPS data.
The Proba-3 mission is set to become the first in the world to conduct high-precision formation flying in space. The two satellites, named Occulter and Coronagraph, will synchronize their flight to form a sizable virtual rigid structure, with a precision measured in millimeters and arc seconds, capable of responding to rotation and directional commands.
By manipulating the distance between the satellites, which can vary from 25 to 250 meters, Proba-3 will cast a controlled shadow, effectively unveiling the Sun's corona. The twin systems, weighing 350 kilograms and 200 kilograms respectively, will simulate a singular, large telescope in space.
This mission is not just a technological trial but will also carry a coronagraph instrument, divided between the satellites, to capture images of the solar corona. The goal is to validate this formation flying technology end-to-end, presenting a more cost-effective solution for future space telescopes that require large, precisely aligned components without the need for cumbersome unfolding structures.
In essence, Proba-3 stands as a precursor to a new generation of space missions, driving innovation by demonstrating a scalable, precise, and potentially more cost-efficient approach to space-based observational technology. With its successful environmental testing now complete, the mission is poised to take the next step toward its highly anticipated launch and operation in the vast theatre of space.
Analyst Summary:
The ESA's Proba-3 mission embodies a significant leap in space mission design and technology. For a Space Industry Analyst, this mission is of high relevance, scoring 9 out of 10, as it promises to pioneer precision formation flying, which could revolutionize the design and functionality of future space missions. This innovation has the potential to enable more sophisticated observations and satellite operations without the prohibitive costs of large monolithic spacecraft structures.
From a Stock and Finance Market Analyst's perspective, the score is 6 out of 10. The direct financial implications of the mission may not be immediately evident, but the project's success could positively influence the stock valuations of involved companies like Sener and GMV. It signifies the growth of a market segment dedicated to advanced space technologies, which could attract investment and potentially lead to a revaluation of aerospace entities participating in or supporting such technological advancements.
A Government Policy Analyst would find this article to have a 7 out of 10 relevance, as the mission aligns with governmental interests in technology leadership, international collaboration, and the advancement of space exploration capabilities. The policy implications extend to international cooperation, funding for space science and technology, and the strategic positioning in space exploration and utilization.
The Proba-3 mission is a testament to the significant events and trends in the space sector over the past 25 years, reflecting the evolution from single-satellite missions to more complex, multi-satellite formations. It correlates with the trend towards miniaturization, increased autonomy, and international collaboration seen in missions such as the International Space Station and numerous Earth observation constellations.
However, there are discrepancies when compared to earlier years where space endeavors were largely dominated by single, large spacecraft built by individual nations. The shift towards consortia of industry specialists from multiple countries is a notable similarity to current trends in the space sector, reflecting a globalized approach to tackling space exploration challenges.
Investigative questions analysts might consider include:
1. How will the technology demonstrated by Proba-3 be applicable to other types of missions, such as deep-space exploration or Earth observation?
2. What are the projected cost savings for future missions using technologies validated by Proba-3 compared to traditional spacecraft design?
3. How will the successful deployment of the Proba-3 mission influence funding and policy decisions for future space technology programs?
4. In what ways could the advancements from the Proba-3 mission be commercialized for broader industry application?
5. What are the potential cybersecurity concerns with the increased autonomy and complex operations of formation-flying satellites, and how are they being addressed?
Quelle: SD
----
Update: 4.04.2024
.
Solar Orbiter prepared for ‘worst-case scenario’
In-depth
Mission control to Solar Orbiter. Come in Solar Orbiter…
“It’s our worst-case scenario,” says flight controller Daniel Lakey. “If Solar Orbiter were to experience some major issue on board, and then we were unable to reestablish communications.”
Solar Orbiter’s close approach to the Sun ('perihelion') is a period of peak scientific activity.
It requires flight control teams and flight dynamics experts at ESA’s ESOC mission control centre to carry out a series of highly complex operations.
If something goes wrong during these activities, the spacecraft could auto-reset itself into ‘safe mode’.
In safe mode, the spacecraft’s software restarts and only its most basic functions are reactivated. Teams on Earth then work out what triggered the safe mode, solve the issue, and restart more advanced systems like scientific instruments.
A safe mode during perihelion would be particularly bad because of the severe impact on science operations during this busy period.
Solar Orbiter also has less power available during perihelion as the intense heat requires it to tilt its solar arrays away from the Sun in order to avoid damage.
The spacecraft must be recovered as quickly as possible before science is lost, or worse, it runs out of power.
The stars guide the way
“The Sun is so bright that even a basic Sun sensor is enough to make sure that Solar Orbiter always knows where the Sun is and can always point its heat shield towards it. This sensor activates during safe mode and keeps the spacecraft’s internal systems safe from the radiation emanating from our star,” says Lakey.
“So, we know that Solar Orbiter will always point its ‘front’ towards the Sun. But to work out which way ‘up’ it is, we rely on star trackers.”
The top priority for a spacecraft in safe mode is to point its communication antenna towards Earth and reestablish contact as soon as possible.
The star trackers switch on automatically during safe mode and the spacecraft uses them to recognise certain patterns of stars. It can then determine its orientation, and in which direction it should point its antenna to communicate with Earth.
“But if the star trackers fail to lock on to the right stars, or the recovery sequence is interrupted before they can be switched on, Solar Orbiter has no way of knowing where Earth is.”
Spinning into control
To make the situation even more challenging, in safe mode, Solar Orbiter can only use its back-up communication antenna.
The back-up antenna can move ‘up and down’ in one axis, but not ‘left and right’ in the other. This prevents a number of potential complications, but it also means the whole spacecraft must rotate in order to point the antenna in certain directions.
The solution is ‘strobing’ – if Solar Orbiter ever finds itself in safe mode and unable to locate Earth, it will begin to roll around one axis while keeping its heat shield pointed safely at the Sun.
“In strobing mode, Solar Orbiter emits a signal with a special ‘tone’ – a beacon in the darkness of space,” says Lakey.
“Eventually, this signal will sweep across Earth. As soon as we detect it at one of our ground stations, we can assess the situation, work out what caused the safe mode and carry out our problem solving and recovery operations.”
That’s the theory, anyway. During Solar Orbiter’s four years in space, it has never had to rely on a strobing recovery – and it has never been tested in flight.
Until now.
The teams at ESOC used a recent period of low communication delay with Solar Orbiter to test whether they are ready to handle a real strobing recovery.
“We began to spin Solar Orbiter around and see if we could detect the beacon from the back-up, antenna,” says Lakey. “We preloaded commands to return to normal operations in case we failed to detect it, so there was never any risk to the spacecraft.”
The recovery tests were a success. The teams confirmed that they could detect Solar Orbiter's emergency beacon and identify the status of the spacecraft in the event of a safe mode with malfunctioning star trackers.
These are the first vital steps in regaining control of the spacecraft and demonstrated the team’s readiness for this critical but unlikely scenario.
“We also successfully tested our ability to communicate with the satellite in particularly tricky situations, such as when its own heat shield partially obscures the antenna’s view of Earth.”
This is just one of hundreds of potential issues that our teams dream up and plan for every day. ESA’s missions are unique one-of-a-kind spacecraft: they may face problems that no other spacecraft ever has.
There are few similar examples to learn from, and few established procedures to follow. It’s essential to test our spacecraft recovery operations in space and for the teams on Earth to practice them when they have a good opportunity.
“We’ll never stop thinking about new challenges that our missions could face,” says Lakey. “Or about how we would overcome them.”
Quelle: ESA