Wednesday, June 21, 2017

What NASA Astronomers Do - observational specialist graphs his career and the history of the science

Dr.Ted Gull,astronomer emeritus at the NASA Goddard Space Flight Center in Greenbelt,Maryland,described what it has been like to be an astronomer for the past 50 years-perhaps a harder job than people think-to a handful of astronomy buffs at C.Burr Artz Library in Frederick,Maryland as part of the library's Discover Space initiative this summer.Dr.Gull has been with NASA for 37 of those years,during which he has authored 597 papers.He is still continuing his research beyond his retirement two years ago.As an emeritus at GSFC,he gets a study carrel in an office he shares with 12 other people,and a computer.He has traveled so widely since retirement,he and his wife have only been home eight months over the past two years.He's been working in Sweden,Italy and Chile,among other places.*
Dr.Gull graduated from MIT in 1966,one of a group of twelve physics majors who went on to get degrees in astronomy.In the 1960s,he pointed out,photo diodes were used to measure the light of a star,one star at a time.Images were captured on 14x14 glass plates coated with a photo-sensitive emulsion-at Mt.Palomar,California,for instance,home of the then stupendous 200-inch Hale Telescope.Spectrographs were then,as they are now,one of the major tools that astronomers use.A spectrograph is a device that separates light into its wavelengths and records the data,or spectrum.University of Wisconsin astronomer Blair Savage put it this way:
A picture may be worth a thousand words;but a spectrum is worth a thousand pictures.*
Until the 1980s,Dr.Gull recalled,astronomy was very laborious,carried out in very cold conditions at night.Astronomers often worked 18 hour days preparing observations,calibrating telescopes,making the observations at night,developing and cataloging the photographic plates.It was like this until the advent of the CCD solid state devices,or charged coupled devices,which directly recorded the images,read them electronically,and provided data for processing by computer.We are developing new CCD detectors every day for future missions-and they have many military applications as well.*
The early space telescopes were OAO-1 and OAO-2 (Copernicus).Such astronomy projects took months,years-even decades-to develop.They were computer-controlled,but with primitive computers at first.The iPhone 7 is a thousand times faster than those computers were.Eventually,however,as technology progressed,observatory observations started being made in university offices hundreds or even thousands of miles from the actual telescopes.Yet even today someone still has to be on site at the observatory to operate the telescope,make sure it's working right and make weather observations.You still need clear skies for observing.*
The International Ultraviolet Explorer Telescope lasted for 18 years,from 1978-96,until its funding ran out.It was the first remotely interactive observatory.From its data,thousands of published papers and over 100 PhD theses were generated.Indeed,papers based on its data are still being written to this day.*
Dr.Gull worked directly with the astronauts for two years between the Apollo and Space Shuttle eras,preparing them for Space Shuttle astronomy projects.*
The Astro-1 space telescope was attached to the Space Shuttle.Dr.Gull was chief scientist of the mission.It was the mission from hell,Dr.Gull joked.Initially,it was to be on five different shuttle missions,and two astronomers were to fly on the shuttle as mission specialists.Dr.Gull removed himself from consideration for becoming an astronaut-a decision he doesn't regret.The Space Shuttle Challenger accident led to a hiatus of four and a half years for Astro-1,but it finally got to fly on 2-11 December 1990,and a second time five years later,which went beautifully.Astro-1 was beset by hardware problems,but they were all resolved.In the end,Astro-1 got 50% of the observations they had hoped for,and its data generated 100 papers.*
The Hubble Space Telescope was conceived by Lyman Spitzer in the 1940s as a way to circumvent the murkiness of the Earth's atmosphere,as you cannot see ultraviolet radiation through the atmosphere.Launched in 1990,it is still operational after 26 years in orbit.Its mirror is 2.4 meters in aperture.HST needed periodic upgrades and repairs.The correction of lenses and mirrors were needed;and gyros,computers and solar panels had to be changed over the course of five servicing missions.The last repair mission was in 2009,and HST is still working beautifully.
The HST mirrors were modified so as to fit in with the spy satellites the shuttle had to carry as well,Dr.Gull noted.HST is expected to be in orbit until the 2030s.It has a 96 minute orbit and is traveling at 18,000 mph.During its life,we have gone from reel-to-reel tape to all solid state memory.
Everything that goes up into space still has to be radiation-hardened,Dr.Gull added.It takes up to ten years to devise hardening for something.*
NASA's James Webb Space Telescope will be launched in 2018 from French Guiana on a European Space Agency Ariane V rocket,which demonstrates the international nature of the programme.It is named after James Webb,the first administrator of NASA.Dr.Gull actually met James Webb and feels that he was a visionary.While Dr.Gull has been photographed next to the JWST,he isn't directly involved with it.Its mission is to peer back to the first stars and galaxies in the universe,in the first 300 million years of the universe's existence.Its mirror is 6.5 meters across.*
As for his own research,there is a nebulous,or gaseous,region in the constellation Orion.Dr.Gull noticed that one of the Orion nebula's stars has an arc around it.That means the star has a wind.The star is moving through an ionised region of the nebula,creating a bow wave.Stars have massive winds,and there are over a dozen examples of this.
His favourite celestial object is the Eta Carinae binary star system.It is a Southern Hemisphere object.Eta Carinae is a massive binary that is nearing the end of its life.Eventually,two supernovae will result from it.Why is this binary so important?The first stars that formed in the universe were massive,and most likely binaries,Dr.Gull explained.This binary system is producing huge amounts of Nitrogen.Our own bodies are made of such star stuff,so we are trying to understand ourselves when we learn what the first stars were like,and how they enrich the interstellar medium.
Dr.Gull continues to do his research using the Hubble Space Telescope and Chandra X-ray Observatory,as well as the Atacama Large Millimeter Array radio telescope in Chile.Such is the life of discovery of a sharp scientific mind engaged in NASA astronomy.

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