- Posted December 3, 2012 by
Arnold Air Force Base, Tennessee
This iReport is part of an assignment:
Your views of space and stars
AEDC played a critical role in supporting NASA Explorer's mission to MAP the skies
Looking skyward, scientists world-wide now know the universe’s size, composition, approximate age and rate of expansion, thanks in part to “essential” data derived from a time-sensitive test conducted at the Arnold Engineering Development Complex’s (AEDC) Mark 1 Aerospace Space Chamber in February 2000.
On June 30, 2001, a Delta II launch vehicle carried NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) on a mission to make fundamental measurements of cosmology – to literally study the properties of the entire universe.
A story recently posted about the probe’s significance to the scientific community on NASA’s website caught the attention of Jim Burns, AEDC's Space Chambers lead.
“The solar arrays for NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) were tested in Mark 1 during the late 1990s or early 2000,” Burns said. “NASA’s recent story regarding this particular project, like others we’ve supported with testing at AEDC during the 1990s and into this decade, shows the impact our work is having on research today.
"Many years, literally, can transpire between when this type of technology is conceived, developed, and tested at a place like AEDC and before the final mission payoff is realized.
In this case that payoff changed how we view the universe and led to the 2010 Shaw Prize and 2012 Gruber Cosmology Prize awarded to Dr. Charles Bennett. And that mission laid the foundation for subsequent and very important ongoing research and related space exploration."
Bennett, an Alumni Centennial Professor of Physics and Astronomy and John Hopkins University Gilman Scholar, is a physics and astronomy department faculty member at John Hopkins University in Baltimore, Md.
Bennett said AEDC’s role was “absolutely critical” in helping to pave the way for this landmark NASA Explorer mission to “map” the universe and study its properties.
In 2000, Bennett was NASA Goddard’s principal investigator for the MAP project and had tasked Alphonso Stewart to find the best place to ground test the probe’s solar array and deployment equipment.
Stewart, an aerospace engineer with NASA Goddard Space Center’s Mechanical Engineering Branch, was the lead solar array deployment system engineer for the 2000 testing in AEDC’s Mark 1 Aerospace Chamber.
Bennett kept in close touch with Stewart all during the testing at AEDC to monitor the deployment, functionality and survivability of the solar array.
“It would be devastating if it [had] failed, there would have been no recovery from a failure,” Bennett said. “NASA would ask me occasionally, ‘and what if this deployment fails,’ and I would just tell them, ‘end of mission.’
“‘We will get nothing out of it if that happens’ – not the answer they wanted to hear – but it was the truth. Frankly, I leaned very hard on Alphonso and made sure that he understood that this had to work. This was not a best effort, this had to work.”
Stewart, who is currently NASA Goddard’s lead deployable(s) engineer for the James Web Space telescope, said finding and then choosing AEDC’s Mark 1 Aerospace Chamber as the site for the test paid off in more ways than his team had envisioned.
“At the time, we needed a facility large enough and cold enough to check the functioning of the array,” he said. “That system is both a solar array as well as a thermal shield, it actually shields the spacecraft from the sun, so it get can get very cold.
“For example, when facing the sun, the shield is designed to attenuate the heat it generates down to minus 150 degrees [Celsius], and Arnold’s [Mark 1] facility had the ability to go to minus 200 at the time. So, we were able to test the shield in that very cold environment.
“We didn’t know this [at the time], but we found out that the blanket was so efficient in its ability to reject heat that just within the 30 or 40 seconds of deployment, it changes 100 degrees. We did not calculate that, we just actually saw that in the test.
“And by knowing that, we were able to adjust the size – to make extra material in the blanket because as it deploys, it’s shrinking. So that when it does get to the end of the deployment, there is still enough material to allow it to open up. Not knowing that, you would have had a problem when you got on orbit, the system just wouldn’t open up properly.”
Bennett said after his team had searched the country for a facility to test their equipment, he is grateful for the support provided by AEDC and their team on that history-making test.
“This satellite [WMAP] has made the most accurate measurement of the age of the universe and that made the Guinness Book of World’s Records,” Bennett said. “13.7 billion years old – when I was in school, didn’t know if it was 9 billion or 22 billion – now we know the age of the universe to one percent.
“It’s an extraordinary change and we also now know the results of this satellite about the components of the universe; the contents. For example, your body is made of atoms, mine is, we all are, your chair is made of atoms, and the Earth is made of atoms.
“You might normally think of everything in the universe as made of atoms, but it turns out, according to the measurements [provided by] this satellite, that the atoms are only 4.6 percent of the content of the universe, actually a tiny amount.”
Bennett, continuing, said, “Five times more than the atoms, there’s something that we call cold, dark matter. This is a kind of material that has gravity, but it doesn’t give off any light at all. That’s why we call it dark matter. We can tell it’s there by its gravity, but not by giving off any light.
“The biggest missing piece of the pie is something that was only recently discovered called dark energy. A Nobel Prize last year was given to the discovery of this dark energy. This satellite actually helped those guys get the Nobel Prize because we showed that the dark energy was there and that it’s 73 percent of the universe.”
Bennett said the dark energy “acts like an anti-gravity, it pushes the universe apart.”
He emphasized that it will take more work to determine what the dark energy and dark cold matter are composed of, “but we do know from this satellite about the percentage that each of these make up, the pieces of the pie.”
Bennett said it also helps to understand how the WMAP functioned.
“The probe was somewhat like a radio receiver,” he said. “In the old days, we used to get our radio and TV signals as electromagnetic spectrum waves received and routed to analog receivers, not digitized signals like we get through cable or routed from satellites. And between stations or channels, we had something we called snow or noise. It turns out that one percent of that is actually from space. That’s from the beginning of the universe, one percent of that static.”
Caption for 121009-O-0000U-915: This artist' rendering – a timeline of the universe – shows a representation of the evolution of the universe over 13.7 billion years. The far left depicts the earliest moment we can now probe, when a period of "inflation" produced a burst of exponential growth in the universe. (Size is depicted by the vertical extent of the grid in this graphic.) For the next several billion years, the expansion of the universe gradually slowed down as the matter in the universe pulled on itself via gravity. More recently, the expansion has begun to speed up again as the repulsive effects of dark energy have come to dominate the expansion of the universe. The afterglow light seen by WMAP was emitted about 380,000 years after inflation and has traversed the universe largely unimpeded since then. The conditions of earlier times are imprinted on this light; it also forms a backlight for later developments of the universe. (Photo courtesy of NASA/WMAP Science Team)
Caption for 020215-O-0000U-407: Ricky Bush, an ATA lead machinist for Arnold’s space chambers test cells, watches the removal of the NASA/God...