Successful All Foothill IEEE Students Forum Meeting Held April 20
|May 21, 2013||Posted by COMauthor under COMSOC, General||
Saturday April 20, 2013 was an opportunity for over 90 students from our IEEE Foothill Section engineering schools ,plus three students in Astronomy from NotreDame HS Riverside, to meet together an hear a report on the James Webb Space Telescope(JWST). The morning was spent on briefings from the Chief Engineer and a Senior Scientist from Northrop Grumman describing how engineering is done on this large multi-national program. The afternoon was devoted to the various IEEE Student Branches giving a survey of their activities over the past year.
Dr Rolf Danner started off the morning giving an overview of the James Webb Space Telescope program. He explained the meaning of energy in the Infra-red (IR) frequency bands, and why the JWST is designed with IR sensors so as to see the cold objects in the universe that are far distant from us. He displayed images showing the similarities and difference between JWST and the now flying Hubble Space Telescope. No surprisingly, JWST will be much bigger in size, ant its mission will be to obtain data on stars and other material in space out to the time frame of 98% of all spatial objects created since the Big Bang. He showed multiple photos of the JWST taking form in the laboratory at Redondo Beach, and when various components will be built and integrated into the final telescope. He showed multiple images of the kapton heat-resistant material selected for the sunshield, and how it is “stretched ” onto its form.
Following Dr Danner was Dr Jon Arenberg, the Chief Engineer. He immediately picked up the thread that connected the JWST program requirements directly to the engineering requirements. As summarized from the Science Requirements Documents, the science requirements state that the objects/ space targets will be:
(1) faint(weak signals from very distant stars /moving sources);
(2) small( very limited angular extent);
(3) distant( IR part of the Plank Black Body energy distribution curve);
(4) random location(may be located anywhere in the sky or galactic space).
These science requirements point to the very top level of engineering needs, which then have to be translated into engineering requirements. The JWST will then have to be:
(1) Big in special extent (to capture as many photons in the IR band as possible per unit time);
(2) Cold (much colder that the surrounding space so as to improve and maintain the sensitivity of the IR signal solid state detector);
(3) Stable (the JWST must maintain a stationary position in space during the long collection aperture time);
(4)Diffraction limited at 2 microns wavelength (baseline for the sharpest imagery set at a point in the IR band);
(5) All Sky viewing capable (JWST is planned for a long viewing life for collecting data in space).
As Dr Arenberg indicated, these top level needs for the JWST were translated into macro-requirements, then into micro requirements, and then finally into the continuing revolving nano-requirements. Each level in turn means that engineers have to solve more detailed problems, and verify that their solution addresses the proper requirement, and that it solves this requirement.
As an example, Dr Arenberg showed how he had addressed the issue of verifying how much sunlight will get to the inner layers of the sunshield at the specified maximum tilted angle with respect to the sun. JWST will be launched, and maneuvered to the stationary L2 point, about a million miles from Earth. The sunshield, with its five layers of kapton membrane extended, will be facing the sun. This sunshield will be receiving 200,000 watts of energy. On the other side of the sunshield, where the instruments are located, there should only be 0.85 watts of energy. This means that the sunshield must perform as designed, and reflect the hot sunlight. Dr Arenberg looked at the case where the outer layer of the sunshield has a slight offset, and does not extend to its ideal specified location. He set up a model for MATLAB computation, based on solving 3-Dimensional geometry problems, Probability analyses, and Monte Carlo techniques (based upon Ulam and Metropolis earlier mathematical analysis) to investigate. The results were presented as plots of 10 microm wavelength stray light into the inner lavers of the sunshield, versus relative motion of the corners of the sunshield, and the resulting wiggle between these corners. The analysis showed that the specification for the sunshield was met (3 sigma point) at the maximum tilt /viewing angle of 7.3 degrees. This is most important when you have a driving requirement of 1.0 arc second pointing accuracy.
So, our IEEE Foothill Students received an overview of the current major NASA funded program, and gained an insight into how system engineering is done at its best in our morning session. Thank you, Drs Rolf Danner and Jon Arenberg for your presentations, and for answering all our questions in the extended Q& A session. Their explanation of their plans to avoid any Hubble-like issues shows the attention to detail by the entire NGC team that will make JWST a successful program, and will change the face of astronomy and astrophysics for the next two decades.
Afterwards the students exchanged notes and views. The consensus seems to be that we in IEEE Foothill Section, students and professional members alike, should have another All Student Forum next year.