Idle Diffractions

Observations from Society for Information Display (SID) 2010 Exhibition

Just a quick note about SID 2010.  The SID exhibition is a great place to see the TV you want in your living room or bedroom, in about five years.  This year did not disappoint.  The clear, out-and-out winner this year was the LG 84” 3-D Home Theater.  Coming on the heels of Avatar, this unit is stunning for its size, clarity, color saturation, and by far the best 3-D of the show in this size group -- at least that I saw. The other truly amazing unit was an LED TV, about 72 inch format, 3mm thick.  Very cool on the wall.  Often these units never make it to the consumer, but if the LG unit does, it just may find a place in my home.

The best talk at SID, I thought, was the plenary on the history of airplane cockpit design by a veteran Boeing designer (we were in Seattle after all), Mike Sinnett.  He had a photo of the first Boeing cockpit – a single seater, and then a photo series of great moments in airplane cockpits.  He made the interesting point that the parameters of interest are the number of people up front and the number of windows.  This peaked, as I recall, with five people in the front cabin: pilot, copilot, radioman, navigator, and manager. I believe it had seven windows.  The last transition was to convince the union that a move from three to two people, even in the biggest plane, is acceptable. 

A Boeing cockpit in the very near future (from Google Images, search “Boeing & cockpit”,
this particular image is posted at http://sarmtraining.com/images/b787%20dreamliner-cockpit-2.jpg)

With IODC upon us, this is a short entry, but I didn’t want to miss the chance to send accolades to the speaker.  And by the way, to see more interesting Boeing photos, try a Google images search on “Boeing & cockpit”.

The other interesting plenary was from a to-be-unnamed technology company.  A very well prepared marketing plenary tried to convince me that one of my hands is now destined to carry a cell phone that I will squint at for all sources of news and entertainment.  I refuse to believe this is the future of civilization.  This has reinforced my resolve to help bring see-through augmented vision displays to the world, maybe in less than 10 years.

Hope to see you are IODC.  Come up, say hello, get a book and the collected works of David Shafer, and let me know how to keep this little site interesting and relevant to you (or, just e-mail me).

What if you could adjust the “filter” on your eyes?

For those in science, and particularly those in optics, we know that the eye responds to only a limited range of all possible wavelengths that are shooting past us.  We know short of deep blue there is the UV (and skin cancer).  The long of deep red is the infra-red, then eventually heat, and on to radio waves, extending eventually to the water waves on a lake, in a less abstract medium.  What if we had a button that allowed us to see other wavelengths?

Well, electronic detectors, like those on the Hubble Space Telescope (HST), let us do just that.  By encoding wavelength information we cannot see in a spectrum that we can, we can begin to learn what the world, and better yet the universe, looks like at other wavelengths, and in fact how much there is to learn.  In fact, one important point when it comes to the universe is that light arriving here from far away is also very old—billions of years.  Light travels fast enough to circle the earth at the equator about 7 times in a second, but, on the scale of the universe that is actually pretty slow.  This old light is red-shifted (I am not going to cover this today), meaning, even if it starts out blue, by the time it gets here, it is not even red—it is deep in the infra-red. 

Subsequently, the new James Webb Space Telescope (JWST) , designed to routinely look to and try to understand the edge of the universe, and therefore the edge of time (and no, I’m not going there today either), will have detectors that are designed to only see infrared light that we cannot ourselves “see”.  Starting at a large scale with the space-based telescopes of the last 20 years, we have been building a massive database of information in colors that we cannot ourselves see, including x-Ray (Chandra) and deep Infra-red (WISE).

That brings us to today’s “find”, which comes to us from ORA’s Mark Kahan.  It came to Mark from a friend, Art Ferruzzi, who is always on the lookout for interesting Internet articles in science.  There is now a web-link where you can call up regions of the sky/universe and dial in the wavelength bands you would like to “see”.

www.chromoscope.net

Somewhat reminiscent of recent photo reconstructions of space where they remove the “new” objects and leave only the really “old” ones, this view of our universe is truly inspiring.

It so reminds me of something I was once asked in high school, as I was labeled as the science kid in the group.  My friend from the age of 4 said to me, “I really hope I get to travel into outer space and go to another planet to see different colors”.  That was somewhat a confused view of the world, but, I will be forwarding this website to him next and let him know his wish has been granted, more or less.

Since we always like to have a graphic, this is one of my favorites, as I was not able to copy off of the live site successfully.  On the left, the darkest region in space over the format of the Hubble Space Telescope as seen from the ground in ultra-deep exposure mode (i.e., a region with the least number of objects).  On the right, the same region shot with the Hubble following the 1st repair mission.  Soon to be surpassed, I believe, by the new equipment.  If anyone happens to spot a new shot of this region, do let me know.

NASA’s Wide-field Infrared Survey Explorer (WISE)

Today Mark Kahan, ORA’s Chief Electro-Optical Systems Engineer, has contributed a short Guest Blog on NASA’s Wide-field Infrared Survey Explorer (WISE).   

Mark is a Member of the WISE Standing Review Board, and, among other areas, he was involved in a number of different aspects of the Hardware, from Design through Test, and on to Cover Deployment and On-Station Performance. Many of the WISE Lessons-Learned J, over various Engineering & Managerial aspects, will be covered at the SPIE’s Annual Meeting in San Diego on 1 August 2010 as part of a broader Session entitled “An Optical Believe It or Not: Key Lessons Learned”.

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The WISE mission was competitively selected under NASA's Explorers Program which is managed by the Goddard Space Flight Center (GSFC), Greenbelt, Md. The Science Instrument was built by the Space Dynamics Laboratory, Logan, Utah, using a Cryogenic Telescope, Aft-Optics, and Scan Mirror (shown to the right) built by SSG-Tinsley/L-3 Communications, Wilmington, MA, and the Spacecraft was built by Ball Aerospace & Technologies Corp., Boulder, Colo. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena, under the watchful eye of Ned Wright, the WISE Mission Principal Investigator (PI). Caltech manages JPL for NASA, and JPL was the Lead NASA Center relative to the responsibility of insuring the Hardware was built-to, and is performing to, Specifications (see http://www.jpl.nasa.gov/wise/)

WISE launched Dec. 14, 2009, from Vandenberg Air Force Base in California, and it will spend nine months scanning the sky in infrared light, revealing all sorts of cosmic characters—everything from near-Earth asteroids to young galaxies more than ten billion light-years away. Before the Mission ends it should uncover hundreds of thousands of asteroids, and hundreds of millions of stars and galaxies. Its vast catalog of data will provide astronomers and other missions with data to mine for decades.

Because so much has been written about WISE, this Blog will concentrate on providing a bit of added insight into the WISE First Light Image, and in doing so we can see why WISE has astronomers so excited.

Before WISE launched, this is what we could see at 3.5 microns in one area of the sky about three times the size of the full moon:

We could see a bit more at 12.5 microns:

 
Then we opened up the WISE Cover, and this is what we saw in the same area of the sky:

 
The 1st light WISE picture shown above was taken looking at the constellation Carina which is near the Milky Way (about 5 degrees out of the plane of our galaxy called the ecliptic). We were Nadir pointing  (i.e. we were pointing away from the earth, which is important so as to keep WISE cold), and we were in the Southern Hemisphere, probably over South America. We were staring at one region of the sky by controlling the S/C reaction wheels. Though this first image was captured as the spacecraft stared in a fixed direction in order to help calibrate the WISE pointing system, the mission's survey is being done while the satellite continuously scans the sky, and an internal scan mirror counteracts the S/C motion to create 8.8 second freeze-frame images.

The "first-light" picture shows thousands of stars and, as was noted above, it covers an area ~ three times the area of the full Moon (WISE’s FOV is about ¾ of a degree by ¾ of a degree – actually 47 arc-sec, and the Moon is ~ ½ Degree). Eventually, if nothing goes wrong, WISE will take more than a million similar pictures covering the whole sky.

The first light picture shows infrared light from three of WISE's four wavelength bands: blue, green and red correspond to 3.4, 4.6, and 12 microns, respectively. There’s a 25+ micron band too, but it wasn’t included for convenience and to speed up the processing to get the 1st image out-the-door (3 color printing is common; sometimes folks add a couple of bands into one of the 3 colors to add further information, but that wasn’t done in the first-light image).

The star labeled V482 is a bright M2 Giant [RA (2000.0): 093023.66, Dec. (2000.0): -582143.2] located about 1,000 (1,058 +230/-160) light years away from Earth, and is about 6th Magnitude (5.9, actually) in the visible wavelength region. Also, since it is a red giant star, it is quite a bit brighter in the infrared, almost first Magnitude by the time one gets to 2 microns (it is ~ 0.5 Magnitude in Bands 3 & 4, around 12 microns and 25 microns, respectively). A hot star like Vega will have the same optical and IR Magnitudes, while a cooler star will have brighter (smaller number) Magnitudes in the IR than the visible.

One question that comes up a lot on the WISE 1st Light Image (because it sort of sets a sensitivity threshold for comparison) is “Would the bright star be visible with the naked eye?” The answer is “Yes”. V482 Carinae is barely visible to the naked eye from a dark site. Bigger Magnitudes are fainter, and we usually say the naked eye limit is 6, though some people can see 6.5 and a few can even see 7 (sadly I can see less every year!). Each Magnitude is about a factor of 2.5 in brightness, and 5 magnitudes is exactly a factor of 100, so a Magnitude 1 or first Magnitude star (which is about what stars like the Belt of Orion or the Big Dipper are) are 100 times brighter than 6th Magnitude stars.

With 5-sigma surety, for hot stars with no IR “excesses” (a long discussion in and of itself), WISE can see down to < 16th Magnitude in Band 1, < 15th Magnitude in Band 2, < 11th Magnitude in Band 3, and under 8th Magnitude in Band 4.

Because this V482 star is at declination -58 degrees, you need to be at latitude -58 degrees for it to come overhead, and you can't see it all from the ground if you are north of 32 degrees latitude on Earth (which is the case for both Pasadena at 34.15 degrees, and Boston at 42.32 degrees).

Finally, WISE Pixels are 2.75 arc-seconds in size at the shorter 3 wavelength bands, but we agglomerate 4 pixels (so we’re 5.5 arc-sec by 5.5 arc-sec) at 25+ microns. The FWHM in the shorter bands is ~ 6 arc-sec and it varies over wavelength (in Noise Pixel/NP Terms we run from 12 to 40 NPs over wavelength band, at least when we’re staring; things go up a smidge when we’re scanning).

It’s great to see thousands of the tiniest of details come together in such a great way. Go WISE! J

 -Mark Kahan

Another Exciting New Telescope is Operational in Space WISE

In case you missed it, as many have been saying, there is a new, significant telescope now operational in space.  The “first light” photos have been posted at

http://wise.ssl.berkeley.edu/gallery_first_light.html

and one is shown here.

To get some background on the telescope, there was an article in the LA Times earlier in December (that I missed, but Frank Moreno of ORA passed along.  That link is

http://www.latimes.com/news/nationworld/nation/la-sci-wise10-2009dec10,0,5846611.story

Both sites are worth the 5-minutes. 

ORA’s own Mark Kahan was heavily involved with this program.  One of his recent roles, which is a somewhat obscure, but essential, corner of science is to ensure that all the necessary conditions are met to be sure the protective cover on the telescope actually does come off.  A problem encountered in an earlier test of an important space asset.  I’ll see if I can get him to write something on this, some time soon.  In the interim, enjoy the photos of space.

WFPC2 and COSTAR on Display

COSTAR
Corrective Optics Space Telescope Axial Replacement (COSTAR), "Contact Lenses for the Telescope," on display at the new "Moving Beyond Earth" gallery in the National Air and Space Museum's Mall building.

Image Number: WEB11281-2009
Credit: Photo by Eric Long/NASM
Copyright: Smithsonian Institution

 

 

 

In a May service mission, the systems WFPC2 and COSTAR were brought back to Earth.  WFPC2 is the oversized digital camera that recorded so many of the Hubble Space Telescope’s iconic images after its installation by shuttle astronauts in 1993. COSTAR is the other optical system that was installed in HST on that same first service mission. Its carefully designed and fabricated mirrors “popped out” into precise locations in the optical path to compensate for the famous error in Hubble’s primary mirror, allowing the originally installed science instruments to “see” sharp imagery from the telescope (WFPC2’s design incorporated its own correction and didn’t use COSTAR).

Now the camera that photographed so many stars is something of a “star” itself, on display in the main space gallery at the National Air & Space Museum in Washington, DC. And COSTAR is there too (pictured above), part of a new exhibit called “Moving Beyond Earth.” 

For more information, see this blog post at National Geographic, this recent article at The Space Review web site, or the press release for the new exhibit.

Notes from a visit to the Large Binocular Telescope

 

Last weekend I had the pleasure of taking an “insider’s” tour of the Large Binocular Telescope (LBT), currently the largest telescope in the world based on baseline (22M) and I believe collecting aperture (although it’s hard to keep track), at 2X8.2M.  It was a very nice afternoon and the trees at the peak (10,200’) had turned a brilliant fall yellow.

Since one of my first experiences in optics was to star test one of the last of the six original mirrors in the Multiple Mirror Telescope (MMT) on Mt. Hopkins south of Tucson, it was quite a reset to view how massive the LBT building is compared to the original MMT building, which can be seen from the LBT.  At one point we trekked all the way to the roof (OK, a lot of the trek involved a series of elevators), which is over 200 feet off the ground, to an unseen tiny cement escarpment that provides an amazing view back to Tucson and beyond.  In that we are recently applying nodal aberration theory to these telescopes, it is an interesting perspective to look at an 8.2M mirror and then contemplate the question, what does a 10-micron decenter actually mean?  With these mirrors, there is no absolutely smooth edge circular aperture to measure from.  These are spin-cast mirrors made at Roger Angel’s lab in Tucson and as such the edge is good, but is not a micron-level reference surface.  The experience reminds me of when I worked on an Air Force conformal optics project.  We kept asking for the wing profiles to a number like 10 microns.  The Air Force finally decided the best response was to put us on a plane to St. Louis, where we learned airplanes are made pretty much the same way as a Grumman canoe, containing over three miles of wire.  They do not work well as an optical reference surface.

Additional LBT informational websites are shown below:
http://medusa.as.arizona.edu/lbto/
http://en.wikipedia.org/wiki/Large_Binocular_Telescope
http://www.aip.de/groups/lbt/
http://planetquest.jpl.nasa.gov/lbti/lbti_index.cfm (very short)
 
YouTube video:
http://www.youtube.com/watch?v=rtOyCcJtzcw

I came across a website titled, “100 Hours of Astronomy,” which was created in the spring of this year as part of the global celebration of the 400th anniversary of the first use of an astronomical telescope. I did not spend much time there, but it appears to be a tremendous series of on-site interviews with astronomers at telescopes around the world. I look forward to taking some time to explore the website – enjoy!

100 Hours of Astronomy main page:
http://www.100hoursofastronomy.org/

Optics and the Sun

Solar energy is of growing interest and importance in the world, and optics play a big role. Optical design is needed for concentrating photovoltaic systems as well as solar thermal systems (although the optics in those systems are often a bunch of flat mirrors tracking the sun). ORA’s illumination engineers have been working on a lot of solar technologies the last few years, and we have developed some special software tools to help out with this work.

LightTools image of solar trough system

There are some enormous solar thermal installations operating in Spain and the United States, with more on the way in the next few years. But sometimes improvements in solar energy performance come down to the small things – and making the small things smaller. For example, an article in MIT Technology Review, “More Efficient, and Cheaper, Solar Cells” (http://www.technologyreview.com/energy/23459/), discusses improvements to conventional solar cell manufacturing that could significantly increase the efficiency of multicrystalline silicon cells and bring down the cost of solar power by about 20 percent. This development was announced by a startup company, 1366 Technologies of Lexington, MA. The key to this work is figuring out how to reduce the shadowing and rejected photons caused by metallic conductors on the surface of the solar cell. People have found various ways to do this, but 1366 Technologies claims to be able to do it very cheaply with methods that fit well into standard production processes. They’re looking at increasing cell efficiency from the current typical 15-16% to 18% right away, with hopes of reaching 19% after further development. This has been demonstrated at production scales, not only in the lab.

Hubble's makeover is complete

NASA has just released the first official images from the recently rejuvenated instruments on the Hubble Space Telescope, and they are spectacular.

http://www.nasa.gov/mission_pages/hubble/multimedia/ero/index.html

The new instruments are more sensitive, promising more efficient observations and the ability to look deeper into the past by imaging extremely faint distant galaxies.

The James Webb Space Telescope

The JWST is the telescope that will follow Hubble Space Telescope.  It is something I thought to write about because it is not that easy at the moment to get information about the optics details in particular of the telescope. 

At the just ended 2009 SPIE Annual meeting, I presented my work to create an estimated model of the very complex (from an optical design perspective) NIRSpec instrument being built now, in Europe, for the JWST.  This instrument consists of the JWST (an obscured, field-biased Three Mirror Anastigmat (TMA) followed by a Relay, Collimator, grating, and Camera, each of which is itself an unobscured TMA.  I will write more on this paper at another time. 

• Download "Using Nodal Aberration Theory to understand the aberrations of multiple unobscured Three Mirror Anastigmatic (TMA) telescopes" paper
• Download presentation

The Wide Field and Planetary Cameras of the Hubble Space Telescope, Part 2

The WFPC2, recently replaced in the Hubble by the WFPC3, took many of the most famous pictures of the cosmos. It may be the most famous single camera in history. JPL has recently written a couple of articles on this legendary camera, first installed in the Hubble in 1993. It has been receiving lots of “retirement accolades” recently, some which you might find interesting.

There is a recent article on the return of the WFPC 2 to earth:
http://www.jpl.nasa.gov/news/features.cfm?feature=2163

Accompanied by a multimedia gallery of some of the WFPC 2’s most famous images:
http://www.jpl.nasa.gov/video/index.cfm?id=830

With the last mission to the Hubble space telescope recently completed, successfully, I thought to post my role in the First Servicing Mission, the one that was critical to the overall mission of NASA to keep the public engaged with astronomy.  I had a somewhat unique position in the program and a critical role in the repair (or as they prefer to call it, “servicing”).

I intend to write on this topic over a series of sessions, primarily to provide my somewhat unique view of the servicing mission.  The success of the Hubble First servicing mission had many key contributors, and I was happy to be one of them.  It turned out that this was one of my last major technical contributions before being moved into management.

The Wide Field and Planetary Cameras of the Hubble Space Telescope, Part 1

I have a unique view of the Hubble First Servicing Mission because I was at Perkin-Elmer, the company that made the perfectly wrong primary mirror, during the period when they made the wrong mirror.  As a result, I know first hand the conditions that team was working under.  In this first writing, however, I am choosing to point out something that was nicely featured in the recent PBS program, “400 Years of the Telescope” (http://www.400years.org/). At the time the problem was discovered, the press chose, not wrongly, to feature an early image of M100, a spiral galaxy, showing clearly a very fuzzy image, seen below.

Image courtesy of Space Telescope Science Institute

What they did not point out (at least in my memory), was the much more significant point that because the images were not sharp points, they were spread over multiple pixels and as a result the distance into space from which the Hubble could collect data was, by accident, almost exactly matched to what was already seen from the ground.  As a result, there were no new objects to study, fuzzy or not.  This was shown briefly on the PBS show.  I had earlier assembled the relevant images, which I have been featuring as my “trademark” on all of my presentation title pages for the last many years.

The first image, shown here, was strategically taken from a large ground-based telescope.  It was identified as the darkest point in the sky (field with the smallest number of object with a magnitude as low as 23) over the field of view of the Hubble, as seen from the ground.  As can be seen, this image shows only a few objects, none of which look particularly interesting.  The intent for the Hubble was to move the lowest magnitude images from the 23 as the lowest visible from the ground to around 28.  It was said during the design that if space was considered a 1,000 page book, from the ground we are only able to read page one.

The second image represents one of the longest exposures of the Hubble taken specifically of this darkest region from the ground.  This was taken with WF 2 camera.  This dramatic photo illustrates the success of the Hubble First Servicing Mission.  Nearly every scene in this image has only been imaged by the Hubble and each represents an object that is new to science.  And to think, this is the darkest region in space!

It is not well known actually that the terminology WFPC2 (“whif-pick” 2) actually refers to seven different cameras, in two groupings.  Three of the cameras make up the Wide Field (WF) format and four of the cameras make up the Planetary Camera (PC).  This is illustrated nicely in the following figure.

WFPC2 field-of-view (image courtesy of the Space Telescope Science Institute)

There are four cameras involved with the Planetary Camera, for example, to increase the number of pixels that can be applied to the image.  A four-sided pyramidal prism is used to combine the focal planes optically.  The pyramid physically rotates to switch between the WF and PC format. The “2” meant it was a second-generation camera.

It was very fortunate that it was always planned to replace the instruments as more advanced detectors became available.  One of the biggest problems with these very substantial NASA programs is that the technology that the design is based on is, in this case, over 15 years old by the time it is used.  A lot happens in 15 years.  This was anticipated with the Hubble and interfaces were designed to allow upgrades over the years.