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To contribute to future efforts to locate and study exoplanets, engineers at NASA's Jet Propulsion Laboratory, in collaboration with the Exoplanet Exploration Program (ExEP), are currently working on the creation of Starshade. Once deployed, this groundbreaking spacecraft will aid next generation telescopes by blocking obscuring light from distant stars so that exoplanets can be viewed directly.
Although it may sound simple enough, Starshade will also need to seriously engage in training flying in order to do its job effectively. This was the conclusion of the Milestone 4 report from the Starshade Technology Development Team (aka S5) – available on the ExEP website. As stated in the report, Starshade will have to be perfectly aligned with space telescopes, even at extreme distances.
More than four thousand exoplanets have been discovered to date without the help of Starshade, but the vast majority of them have been discovered by indirect means. The most effective means were to observe distant stars for periodic declines in luminosity indicating the passage of planets (transit method) and to measure the motions of a star to determine the presence of a planetary system (speed method radial).
Although they are effective at detecting exoplanets and obtaining accurate estimates of their size, mass, and orbital period, these methods are not very effective in determining surface-like conditions. To do this, scientists must be able to obtain spectrographic information on the atmospheres of these planets, which is essential to determine if they can actually be habitable.
The only reliable way to do this with smaller, rocky (or "Earth-like") planets is direct imaging. But since stars can be billions of times brighter than the light reflected by the planet's atmosphere, this is an extremely difficult process to complete. Enter Starshade, which would block the bright light of the stars using a shade that would unfold like petals of a flower.
This will greatly improve the chances of space telescopes to spot planets that revolve around a star. However, for this method to work, both spacecraft will have to stay aligned within one meter (3 feet), while traveling at a distance of 40,000 km (24,000 mi). If they are
As JPL engineer Michael Bottom explains in a recent NASA press release:
"The distances we're talking about for Starshade technology are pretty hard to imagine. If the star starred to the size of a drinking glass, the telescope would be about the size of an eraser and would be about 60 miles apart. [100 kilometers]. Now imagine that these two objects float freely in space. They are both facing these small tugs and kicking from gravity and other forces, and at this distance we try to keep them both perfectly aligned at a distance of about 2 millimeters. . "
The Milestone 4 S5 report focused on a separation distance of 20,000 to 40,000 km (12,500 to 25,000 mi) and a grade of 26 meters (85 feet) in diameter. In these settings, a Starshade spacecraft would be able to work with a mission such as NASA's Wide Field Infrared Survey Telescope, a telescope equipped with a 2.4m (~ 16.5 ') main mirror. of diameter and whose launch is planned towards the middle. -2020s.
After determining the necessary alignment between the two satellites, Bottom and his team also developed an innovative way for telescopes like WFIRST to determine if the Starshade had to drift out of alignment. This involved creating a computer program capable of recognizing the moment when the dark and light patterns were centered on the telescope and those that had off-center.
Bottom found that the technique was very effective in detecting the slightest positional changes of a Starshade even at extreme distances. To ensure alignment, his JPL engineering colleague, Thibault Flinois, and his colleagues developed a set of algorithms based on the information provided by the Bottom program to determine when Starshade's thrusters should operate for keep it in alignment.
Combined with Bottom's work, this report has shown that it is possible to maintain the alignment of both spacecraft using automated sensors and thruster controls, even if a larger umbrella and telescope were used and placed. at a distance of 74,000 km. Although revolutionary with respect to autonomous systems, this proposal is based on a long tradition for NASA scientists.
As Phil Willems, head of NASA's Starshade Technology Development, explained:
"This is a good example of how space technology is becoming more and more extraordinary by building on its previous successes. We use formation flights in space whenever a capsule is docked at the International Space Station. But Michael and Thibault went well beyond that and showed a way to maintain training on larger scales than the Earth itself. "
By confirming that NASA can meet these strict requirements for "detection and control of training," Thibault Flinois, a JPL engineer, addressed one of the three technological gaps in the Starshade mission, namely, the relationship between the exact distance and the size of the shade. himself and the main mirror of the telescope.
The WFIRST, one of NASA's next-generation space telescopes to be commissioned in the coming years, will be the first mission to use another light-blocking technology. Known as a stellar coronograph, this instrument will be integrated into the telescope and will allow it to directly capture Neptune images from exoplanets the size of Jupiter.
Although a Starshade project has not yet been approved for the flight, it could potentially be sent to work with the WFIRST by the end of the 2020s. is a step forward to demonstrate that the project is achievable. Be sure to watch this awesome video that explains how a Starshade mission would work, with the kind permission of NASA JPL:
Further reading: NASA
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