Efforts to resurrect the broken reaction wheels on the Kepler space observatory have failed. The spacecraft can still do useful science but not exoplanet transit searches, which requires the extremely stable and precise pointing capabilities provided by 3 working reaction wheels.
Category Archives: Astronomy
Video: Advice on selecting a telescope
The Slashdot technology forum site posted this two part introduction to telescopes for amateur astronomy:
Bruce Berger is an IT guy, but he’s also an amateur astronomer who takes at least one aspect of astronomy more seriously than most sky-watchers. Not content with what he could buy when he first wanted a telescope of his own, Berger set out to make one — it turned out so well, he says he’ll never part with it, and he’s made several others since, and taught many other people to do the same. In this pursuit, he’s also been a long-time member of the Amateur Telescope Makers of Boston, including a stint as the group’s president. (Berger’s custom license plate reads “SCPMKR.”)
In the video Berger discusses what to look for in telescopes.
Amateur Astronomer Bruce Berger Talks About Meteors and Telescopes (Video) – Slashdot
In the next video, Berger continues with advice
on telescope selection and purchasing. He mentions Orion, a telescope vendor he seems to respect, along with other sources for both new and used equipment. Which should you buy (or build): A reflector or a refractor telescope? Bruce talks about how you should make your selection based on what you want to view, your skill level, and how much time and/or money you have available.
Amateur Astronomer Bruce Berger Talks About Telescopes, Part II (Video) – Slashdot
A beginners guide to astronomy
Astronomy newbies should check out the Beginners Guide To Astronomy at Learn Astronomy HQ:
This guide covers how to get started cheaply in astronomy and then progresses to a guide to telescopes and what to consider when buying a telescope. Once you have your equipment the guide covers setting up a telescope, what to start out observing, how to develop your knowledge of the night sky and provides a list of uk astronomy equipment to begin expanding your range and skills.
Three novels with astronomers
In your remaining vacation days of summer, you might check out these novels in which astronomy plays a major role: Holiday reading: The dark glamour of astronomy – New Scientist
The Movement of Stars: A Novel
A love story set in 1845 Nantucket, between a female astronomer and the unusual man who understands her dreams.
It is 1845, and Hannah Gardner Price has lived all twenty-four years of her life according to the principles of the Nantucket Quaker community in which she was raised, where simplicity and restraint are valued above all, and a woman’s path is expected to lead to marriage and motherhood. But up on the rooftop each night, Hannah pursues a very different—and elusive—goal: discovering a comet and thereby winning a gold medal awarded by the King of Denmark, something unheard of for a woman.And then she meets Isaac Martin, a young, dark-skinned whaler from the Azores who, like herself, has ambitions beyond his expected station in life. Drawn to his intellectual curiosity and honest manner, Hannah agrees to take Isaac on as a student. But when their shared interest in the stars develops into something deeper, Hannah’s standing in the community begins to unravel, challenging her most fundamental beliefs about work and love, and ultimately changing the course of her life forever.
Inspired by the work of Maria Mitchell, the first professional female astronomer in America, The Movement of Stars is a richly drawn portrait of desire and ambition in the face of adversity.
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Equilateral: A Novel
Equilateral is an intellectual comedy set just before the turn of the century in Egypt. A British astronomer, Thayer, high on Darwin and other progressive scientists of the age, has come to believe that beings more highly evolved than us are alive on Mars (he has evidence) and that there will be a perfect moment in which we can signal to them that we are here too. He gets the support and funding for a massive project to build the Equilateral, a triangle with sides hundreds of miles long, in the desert of Egypt in time for that perfect window. But as work progresses, the Egyptian workers, less evolved than the British, are also less than cooperative, and a bout of malaria that seems to activate at the worst moments makes it all much more confusing and complex than Thayer ever imagined.
We see Thayer also through the eyes of two women–a triangle of another sort–a romantic one that involves a secretary who looks after Thayer but doesn’t suffer fools, and Binta, a houseservant he covets but can’t communicate with–and through them we catch sight of the depth of self-delusion and the folly of the enterprise.
Equilateral is written with a subtle, sly humor, but it’s also a model of reserve and historical accuracy; it’s about many things, including Empire and colonization and exploration; it’s about “the other” and who that other might be. We would like to talk to the stars, and yet we can barely talk to each other.
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The Falling Sky
Jeanette is a young, solitary post-doctoral researcher who has dedicated her life to studying astronomy. Struggling to compete in a prestigious university department dominated by egos and incompetents, and caught in a cycle of brief and unsatisfying affairs, she travels to a mountain-top observatory in Chile to focus on her research. There Jeanette stumbles upon evidence that will challenge the fundamentals of the universe, drawing her into conflict with her colleagues and the scientific establishment, but also casting her back to the tragic loss that defined her childhood.
As the implications of her discovery gather momentum, and her relationships spiral out of control, Jeanette’s own grip on reality is threatened, finally forcing her to confront the hidden past. Pippa Goldschmidt’s bittersweet debut novel blends black comedy, heart-breaking tragedy and fascinatingly accessible science, in this intricate and beautiful examination of one woman’s disintegration and journey to redemption.
Update on efforts to revive the Kepler spacecraft
The amazing successful exoplanet finding spacecraft Kepler went out of action last May when one of its reaction wheels (basically an electric powered gyroscope) ceased to function properly. The spacecraft has four reaction wheels and needs at least three to point its telescope with sufficient stability and accuracy to carry out the extremely precise measurements of the light of stars. An exoplanet is detected by the slight dimming of a star’s light when a planet transits across the star’s face as seen by the spacecraft.
One reaction wheel had already failed (i.e. friction on the spinning wheel grew too high) and so the failure of the second seemed to ring the death knell of the observatory’s exoplanet searching. However, the team began an effort to determine if one or both of the reaction wheels could be revived to a level of performance that could allow a return to observations for at least some scientific goals if not for exoplanet searching.
Here is a good summary of the status of the recovery efforts: More Efforts to Revive Kepler Space Telescope Mission Planned – Coalition for Space Exploration
And here is the complete statement from the Kepler team:
Kepler Mission Manager Update: Pointing Test
The team has continued exploratory recovery testing of Reaction Wheel 4 (RW4). On Thursday, July 25, 2013, the wheel spun in both directions in response to commands.
While both RW4 and RW2 have spun bi-directionally, friction levels remain higher than would be considered good for an operational wheel. However, it will be important to characterize the stability of the friction over time. A constant friction level may be correctable in the spacecraft’s attitude control system, whereas a variable friction level will likely render the wheels unusable.
With the demonstration that both wheels will still move, and the measurement of their friction levels, the functional testing of the reaction wheels is now complete. The next step will be a system-level performance test to see if the wheels can adequately control spacecraft pointing.
High-precision pointing of the Kepler spacecraft is controlled by reaction wheels,
which are small electric motors mounted on the spacecraft that control
the three axes of motion: up/down, forward/back and left/right. Image Credit: Ball Aerospace
which are small electric motors mounted on the spacecraft that control
the three axes of motion: up/down, forward/back and left/right. Image Credit: Ball Aerospace
The team is preparing for the next test using RW2. Friction levels on RW4, the wheel that failed in May, are higher and no additional testing is planned at this time. The pointing test involves determining the performance of the wheel as part of the spacecraft system. The test will be conducted in three stages.
The first stage of the pointing test will determine if the spacecraft can sustain coarse-point mode using RW1, 2 and 3. Coarse-point mode is regularly used during normal operations, but has insufficient pointing accuracy to deliver the high-precision photometry necessary for exoplanet detection. During coarse-point the star trackers measure the pointing accuracy of the spacecraft. When using wheels to control the spacecraft, pointing is typically controlled to within an arcsecond, with a fault declared if the pointing error exceeds a quarter of a degree. This degree of pointing accuracy would be equivalent to keeping an imaginary Kepler telescope pointed at a theatre-size movie screen in New York City’s Central Park from San Francisco.
In the first stage, testing will demonstrate whether or not operation with RW2 can keep the spacecraft from entering safe mode. A safe mode is a self-protective measure that the spacecraft takes when an unexpected event occurs, such as elevated friction levels in the wheels.
In the second stage, testing will investigate RW2’s ability to help control the spacecraft pointing with enough accuracy to transmit science data to the ground using NASA’s Deep Space Network. If RW2 can sustain coarse-point in stage 1, the second stage of the test will be to point the high-gain antenna to Earth and downlink the data currently stored aboard. This requires that the pointing be controlled more tightly than simply avoiding safe mode, yet does not require the very fine control needed to return to science data collection.
The spacecraft provides the power, pointing and telemetry for the photometer.
Other than the four reaction wheels used to maintain the precision pointing
and an ejectable cover, there are no other moving or deployable parts on
the spacecraft. Image Credit: NASA Ames/Ball Aerospace
Other than the four reaction wheels used to maintain the precision pointing
and an ejectable cover, there are no other moving or deployable parts on
the spacecraft. Image Credit: NASA Ames/Ball Aerospace
The final stage of the test will determine if RW2 can achieve and maintain fine-point, the operating mode for collecting science data. During fine-point the fine-guidance sensors measure the spacecraft pointing. When using wheels to control the spacecraft, pointing is controlled to within a few milliarcseconds. Using our imaginary Kepler telescope example, this degree of pointing accuracy would be equivalent to pointing at a soccer ball in New York City’s Central Park from San Francisco.
The team anticipates beginning the pointing performance testing on Thursday, August 8, 2013 and will continue into the following week if all goes well. A determination of whether Kepler can return to exoplanet data collection is expected a couple weeks after these pointing tests are complete.
As engineers explore recovery of the spacecraft, scientists continue to analyze the existing data. Earlier this week the team delivered their findings for 1,236 new Kepler Objects of Interest (KOIs) to the NASA Exoplanet Archive. The new KOIs were found by searching the observational data from Quarters 1 to Quarter 12. Of the 1,236 new KOIs, 274 were judged to be planet candidates, while many others were determined to be false positives. These newly announced Kepler planet candidates bring the current count to 3,548. Some of these new planet candidates are small and some reside in the habitable zone of their stars, but much work remains to be done to verify these results.
Also announced this week is the Kepler Science Conference II Nov. 4-8, 2013 at NASA Ames Research Center at Moffett Field, Calif. Registration is now open.
Regards,
Roger