Example Assignment Video:
This video is a tutorial that answers the question of the problem with the Hubble Space Telescope and how it was solved. I have uploaded the video on YouTube and the link is here:
Example Assignment Script
Below is the script that I used to create the video.
What was the problem with the Hubble Space Telescope and how was it solved?
According to Chapter 06 of our Open Stax Text, the problem with the Hubble Telescope is that the primary mirror that was used in the telescope had an error in its shape. Our text describes this error as being equal to 1/50 of the width of the human hair.
I did external research on an Australian CIO Website where former NASA Director of Astrophsysics, Charlie Pellerin was profiled. Pellerin calculated this distance as 1.33 MM.
The article quoted him as saying “Holy Christ…In an optical system this is like missing by a thousand miles.”
The incorrect distance led to a decrease in image quality. All the images obtained by the Hubble Telescope were blurry.
Pellerin was called in by his Boss to discuss the problem with these blurry images upon their discovery.
His Boss asked him
“What do you know about spherical aberration?’
“I said all I know is that when amateurs build mirrors and do it sloppily they get what’s called a downturned edge, and on different radii of the mirror it focuses the light on different parts of the optical axis and it’s physically impossible to ever focus a telescope; they’re useless.” The technical term for the phenomena Pellerin described is spherical aberration.
The telescope hubble had metering rods and the ends of these rods were rounded and polished. A beam of light on the end of the rod would then be focused into the center which would provide the correct measurement to center the metering rod with respect to the info meter axis.
A field cap was attached to the end of the rods. Field caps are also known as Dust caps and are intended to keep dust out of a telescope. The instructions for the field cap were for it to be spray painted black.
However, Pellerin says
“The guy was working under great stress because we were angry about costly delays, and were threatening to put Kodak’s mirror in the telescope, which would have been humiliating for our contractor [Perkin-Elmer Corporation was responsible for the mirror]. So he’s working, he’s really hurrying, he can’t find the spray paint. So instead he puts black tape on [the cap] and he takes his X-Acto knife and cuts a hole. He doesn’t notice he made a shiny little burr. So he puts the thing on, the light hits the burr and goes back up.”
“”His instructions were to move the thing in every direction to see if the intensity of the light went down. So he moves it. Light goes onto the black tape, onto the black tape, onto the black tape, down the hole [in the field cap]. He assumes he got it centered.”
“However, the light had hit the burr instead of the top of the rod, which led to a gross misplacing of the two mirrors.”
With all the smart minds working together on this project at NASA, how did this occur?
One of the reasons this happened according to Pellerin is that the project ran over budget. The original budget for the Hubble space telescope was $434 million dollars and by the end of the project the cost was over 1.8 billion dollars. In addition, NASA had created what Pellerin describes as a Hostile environment for Perkin Elmer, their contractor, in which “they told us about any problem at their Peril”.
He attributes the issues with the telescope not to the individual contributors to the project but to the team culture where they took for granted that the mirror was perfect. So everyone assumed the mirror was centered and when there was a problem it was because of the force of gravity in the telescope mount, rather than the problem being that the lens was not centered correctly. Pellerin believes this cultural problem was due to tight deadline and a culture where higher up leaders did not want to hear anything about problems, only solutions.
How did Nasa solve this problem?
Our text explains that the solution is similar to what we do for people with blurry eyes. The same way corrective optics or glasses can correct blurry vision, corrective optics were installed on the telescope.
A more in depth observation of the steps used to correct the telescope optics is found in the Pellerin CIO article.
Pellerin realized that he could fix the problems of the Hubble telescope, because the optics were flawed, but not irregularly so. He used a two billion budget that he was allocated for other projects in NASA, and took 60 million of that to start a servicing mission for the Hubble telescope.
He sent the servicing team to remove an unimportant instrument from the telescope called a High-Speed Photometer.
Once this was removed, they inserted another mirror in the hubble telescope, which was deformed proportionally to the flawed telescope lens. The mirror was called COSTAR which stands for Corrective Optics Space Telescope Replacement. This corrected the error by the time it hit the other telescope instruments (Faint Object Camera, Faint Object Spectograph, and the Goodard High Resolution Spectograph). Like our text, Space and Telescope says that COSTAR acted like a “giant pair of spectacles, refocusing the light and letting instruments see clearly again”.
OpenStax College. (2013). Anatomy & physiology. Houston, TX: OpenStax CNX. Retrieved from http://cnx.org/content/col11496/latest/
Pearce, R. (2012, March 29). What went wrong with the Hubble Space Telescope (and what managers can learn from it). Retrieved August 15, 2017, from https://www.cio.com.au/article/420036/what_went_wrong_hubble_space_telescope_what_managers_can_learn_from_it_/
- (n.d.). History: The Spherical Aberration Problem. Retrieved August 15, 2017, from http://www.spacetelescope.org/about/history/aberration_problem/
By RadioFan at English Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=35454835