The Hubble Space Telescope resumed science observations on Friday after ground teams spent most of the last three weeks assessing the performance of a finicky gyroscope, NASA said.<\/p>\n
The troublesome gyroscope is a critical part of the observatory\u2019s pointing system. Hubble\u2019s gyros measure how fast the spacecraft is turning, helping the telescope aim its aperture toward distant cosmic wonders.<\/p>\n
Hubble still provides valuable scientific data for astronomers nearly 34 years since its launch aboard NASA\u2019s Space Shuttle Discovery in 1990. Five more shuttle servicing missions repaired Hubble, upgraded its science instruments, and replaced hardware degraded from long-term use in space. Among other tasks, astronauts on the last of the shuttle repair flights in 2009 installed six new gyroscopes on Hubble.<\/p>\n
The gyros have long been one of the parts of Hubble that require the most upkeep. A wheel inside each gyro spins at a constant rate of 19,200 revolutions per minute, and the wheel is, in turn, sealed inside a cylinder suspended in a thick fluid, according to NASA. Electronics within each gyro detect very small movements of the axis of the wheel, which supply Hubble\u2019s central computer with information about the spacecraft\u2019s turn rate. Hair-thin wires route signals from the gyroscopes, and these wires can degrade over time.<\/p>\n
Three of the six gyros installed on Hubble in 2009 have failed, and three others remain operational. The three still-functioning gyros are based on a newer design for longer life, but one of these units has shown signs of wear in the last few months. This gyroscope, designated Gyro 3, has always exhibited \u201cconsistent noisy behavior,\u201d said Pat Crouse, Hubble project manager at NASA\u2019s Goddard Space Flight Center.<\/p>\n
Hubble typically needs three gyros to operate normally, so ground controllers shut down Gyro 3 for roughly seven years until Hubble needed it in 2018, when another gyroscope failed, leaving only three of the devices still working.<\/p>\n
,<\/p>\n
\u201cBack in August, we saw issues,\u201d Crouse told Ars this week. \u201cIt would sort of sporadically output some rate information that was not consistent with the observed spacecraft body rates, but it was short-lived, and we were characterizing what that performance was like and how much we could tolerate.\u201d<\/p>\n
The gyro\u2019s performance worsened in November when it fed Hubble\u2019s control system erroneous data. The gyroscope sensed that the spacecraft was changing its orientation when it really wasn\u2019t moving. \u201cThat, then, contributed to an error in attitude that was kind of causing a little bit of drift,\u201d Crouse said.<\/p>\n
Automated software on Hubble detected the errors and put the spacecraft into \u201csafe mode\u201d two times last month. Hubble quickly resumed science observations each time but then went into safe mode again on November 23. Hubble managers took some extra time to gather data on the gyro\u2019s health. Engineers commanded Hubble to move back and forth, and the suspect gyro consistently seemed to work well.<\/p>\n
Recognizing that the gyros are prone to failure, engineers devised a new way for Hubble to keep delivering science data even with one operating gyroscope. In this one-gyro mode, Hubble\u2019s control system would receive inputs from the single gyroscope in combination with magnetometers, Sun sensors, and star trackers. Most of Hubble\u2019s science portfolio would not be affected in a one-gyro mode, but the observatory could have limitations following some faster-moving targets, such as planets, asteroids, or comets in the inner part of the Solar System.<\/p>\n
Hubble uses spinning reaction wheels to torque the spacecraft in large movements from one direction to another. The spacecraft doesn\u2019t have any thrusters to control its orientation or adjust its orbit. There are three fine guidance sensors to maintain a lock on guide stars, keeping Hubble stable during scientific observations. Crouse said Hubble\u2019s ground team is also keeping a close eye on these sensors.<\/p>\n
,<\/p>\n
One of the fine guidance sensors has shown signs of degraded performance in the last two years, he said. A buildup of debris or lubrication along a bearing appears to be the source of some resistance in the sensor, occasionally causing it to stall.<\/p>\n
While Hubble doesn\u2019t match the imaging power and resolution offered by the newer James Webb Space Telescope, the aging observatory still occupies a unique role among NASA\u2019s fleet of science missions. Hubble is sensitive to visible and ultraviolet light, while Webb\u2019s sensors are tuned to detect infrared light.<\/p>\n
NASA wants to keep Hubble going as long as possible. Even if Hubble\u2019s sensors and instruments are still working, aerodynamic drag will eventually bring the telescope back into the atmosphere because the spacecraft doesn\u2019t have any rocket engines. Each of the space shuttle servicing missions boosted Hubble into a higher orbit to counteract the drag.<\/p>\n
Hubble is currently flying at an altitude of around 320 miles (520 kilometers). Current predictions suggest Hubble would reenter the atmosphere in the mid-2030s, but this depends on the conditions of the upper atmosphere, which change with fluctuations in solar activity.<\/p>\n
Last year, SpaceX and NASA announced a feasibility study to determine whether it might be possible for a Dragon spacecraft to link up with Hubble and reboost the observatory, extending its orbital lifetime. This six-month study, which was concluded earlier this year, was also expected to look at ways for astronauts on the Dragon capsule to potentially service Hubble. If a servicing mission is deemed possible, swapping out gyros would surely be at the top of NASA\u2019s priority list.<\/p>\n
NASA and SpaceX have not released the results of the feasibility study. Last December, NASA also released a request for information from other US companies to propose their own commercial solutions for boosting Hubble\u2019s orbit. The agency received eight responses to this solicitation, not including the separate SpaceX feasibility study. In the end, NASA may decide not to move forward with a commercial servicing mission to Hubble.<\/p>\n
Alise Fisher, a NASA spokesperson, told Ars the agency doesn\u2019t have a projected timeframe for completing its review of the Hubble reboost studies. \u201cWe will continue internal evaluations early next year.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"
The Hubble Space Telescope resumed science observations on Friday after ground teams spent most of the last three weeks assessing the performance of a finicky gyroscope, NASA said. The troublesome gyroscope is a critical part of the observatory\u2019s pointing system. Hubble\u2019s gyros measure how fast the spacecraft is turning, helping the telescope aim its aperture […]<\/p>\n","protected":false},"author":1,"featured_media":45655,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[898,190,316],"class_list":["post-45653","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news","tag-hubble-space-telescope","tag-nasa","tag-spacex"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/45653"}],"collection":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/comments?post=45653"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/45653\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media\/45655"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=45653"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=45653"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=45653"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}