AlwaysOn: Bracewell's Observatory

One of the cool things about Silicon Valley is that so many things are invented here, within a 20 mile radius of Palo Alto. But one of the downsides is that you can’t see anything. There’s nothing really historic to latch onto.

Washington D.C. has buildings and monuments, Manhattan has dead spots in the New York Stock Exchange and Alexander Hamilton’s grave. Boston has Faneuil Hall and the Freedom Trail. Even in Milwaukee, you can get a tour of the Miller Brewery.

What do we got? Nothin’.

There is a tiny sign on San Antonio Avenue in South Palo Alto marking the location of Shockley Semiconductor. I almost got into an accident reading it. You can see bean bag chairs at Xerox Parc, if you can sneak in. Cisco was started on Oak Grove Avenue in Atherton, but someone lives there and doesn’t give tours. Sure, we have the Computer History Museum which is fantastic, but dusty old machines pale to something big and majestic.

So here’s my suggestion: drive west on Alpine Road off of Interstate 280, go a mile or so and then turn left just before the tennis courts of Ladera Oaks Swim and Tennis Club. You’ll go over a rickety bridge and then bear right at the nursery. If anyone stops you, tell them Tony Perkins sent you.

You have now entered the Bracewell Observatory. Welcome.

This is not “The Dish”. every radio-astronomers wet dream, a 150 foot diameter, 150 ton parabolic reflector capable of one degree per second tracking sitting on top of a hill with beautiful vistas of the San Francisco Bay. It is involved with such projects as measuring intergalactic hydrogen clouds at L-band, communicating with and commanding the low earth-orbiting OPAL and PICOSAT spacecraft system in UHF, and who knows how many top secret projects. That’s behind you up the hill.

No, no. Instead, you’ll see five rusty 60 foot dishes, forgotten long ago. Until this summer, that is, when Stanford’s Fire Inspector was concerned the place would soon spontaneously combust (this actually happens, it is so dry in the summer that everything has a dead brown look to it). He condemned the area, known as Site 515, and a movement to save it soon jumped into action, demanding meetings with Stanford President John Hennessy, County Supervisors, Supreme Court nominees, the whole nine yards.

What is so interesting about some rusty dishes in Site 515? It’s all in the history. In the late ‘50’s, Ronald N. Bracewell, who is still kicking and I had a nice chat with, was a scientist at Stanford’s Radio Propagation Lab which turned into Space, Telecommunications and Radioscience Laboratory, STAR Lab.

They were running all sorts of experiments on Outer Space, but Bracewell focused on the Sun. In 1956, a year before Sputnik prompted the U.S. to enter the Space Race, Bracewell was building dishes to map the Sun’s surface. He took 32 smallish dishes, 9 meters in diameter and arranged them in a 7.5 meters apart  in a cross pattern. One arcminute if you’re keeping score at home. A single motor, gearbox and two 375 foot long driveshafts moved the dishes in unison so they could track the Sun across the sky.

It took until 1961 to finish, but the dishes began taking measurements of microwaves emitted from the surface of the Sun. Bracewell had all sorts of data, but his goal was a daily microwave spectroheliograph, basically a weather map of the Sun’s surface. This map could then identify active regions and even predict solar flares that might disrupt communications. The Air Force was all over this.

How can you turn all this data, the strength of the Sun’s microwave signals distributed over these 32 cross pattern dishes, into a two dimensional map of the sun’s surface? Not easily. He could painstakingly plot out all the data by hand on graph paper and then calculate what angle the waves left the sun to be able to hit each discrete dish, then use that angle to correct the data from each dish, and then sum up all the calculations for each potential wave on the Sun’s surface and generate one map by the year 2015.

Bracewell’s problem was that there just weren’t all that many computers around in 1961 to do his calculations, certainly no workstations or personal computers he could install at Site 515 to compute his map. That was decades away. So like any good scientist on a budget (and an Aussie at that), he sat down and started working out a solution on the cheap, an algorithm that would cut his computations to a minimum. This is what Fourier Transforms are for. You have to go back to your college calculus class, but a Fourier Transform is an integral function, it converts frequency data into a time or spatial representation.

The basic algorithm that Bracewell started with was first worked out by Austrian mathematician Johann Radon in 1917 – a Radon Transformation that integrated data along parallel lines to reconstruct an object. But Bracewell needed just the surface of the Sun, and introduced the idea of a Filtered Back Projection algorithm.

Think of just seeing the shadow of a tree over time and then working backwards to what the tree looks like in real life. If you had the pattern of waves after they went through the cross section of an object, you do an inverse Fourier Transform, and back into a pretty close approximation to what the object looks like, without doing all that much math.

Bingo. A 33rd dish maybe 375 feet away, another arcminute, was also installed, and helped in his calculations by providing one more set of data for the Transform. Five 30 foot dishes were added for other experiments, and the Bracewell dishes stayed in operation for 11 years, the length of a complete Solar Cycle.

Soon, Bracewell was turning out weather maps of the Sun on a daily basis, which a researcher would fax daily to the Air Force. Then the newly formed NASA found out about it and had to have it. President Kennedy had them putting a man on the moon by the end of the decade, a full employment act for physicists, but a big concern for manned space exploration was radiation from solar flares - microwave bursts would be dangerous for astronauts.

With the Observatory cranking out maps quickly using Bracewell’s algorithms, NASA could warn astronauts of solar flares and have them hide behind radiation shields on spaceships, abort space walks or quickly head inside the Lunar Module instead of hitting golf balls on the moon.

All these dishes were then more or less abandoned in 1972. The smaller 9 meter dishes were sold in the ‘70’s, all that is left is a concrete slap that they sat on. If you go behind the middle dish, you can find the concrete pad. But Bracewell’s algorithm was just warming up.

In 1972, an engineer in England, Godfrey Hounsfield, and a South African physicist working at Tufts University in Massachusetts, Allan Cormack, using Bracewell’s Filtered Back Projection algorithm each independently invented Computed Tomography images, Nobel Prize winning stuff.

X-rays have been used in Radiology since 1895. You blast X-Rays at a body and film is exposed to the X-rays that make it through. Bones are opaque so no X-rays get through (except for broken bones), while organs absorb some of the X-rays, so they show up in various shades of gray. Tomos=slice; graphia=draw. Computer axial tomography, computer assisted tomography, computed tomography, they are all the same thing, CAT or CT scanners.

What Hounsfield and Cormack did was take a series of X-rays images while the X-ray tube was completely rotated around the body. Then using Bracewell’s algorithm, (working backwards from the shadows over time, if you will,) they could create an image which was the close approximation of a slice of the patient’s body. As if you were a magician on the Tonight Show took a hack saw and cut the slice open yourself. A sleight of hand, but this was remarkable stuff.

Without the algorithm, it would have taken forever to reconstruct all of that data into anything useful, but before long, images could be turned out in almost real time, ushering in CT scans, MRIs and turning the field of radiology on its head. What’s going to happen with Site 515? Who knows? Land is scarce and quite valuable in this zipcode. Condos? Graduate housing? Why not? Someone will surely think to flip the dishes a bit and turn them into giant hot tubs. I’d go visit before they pave Bracewell and put in a parking lot.

Andy Kessler is currently working on a book about technology and healthcare. Let him know if you have any interesting tidbits.

Comments

[Lee Courtney]

Yesterday an email from Bob Lash, who has done a great job trying to save Bracewell, showed up saying,

"I just received word that in spite of our best efforts, and in spite of an expected August 4th State hearing to rule on its historical status, Stanford began demolition of the five 60 foot dishes of the Bracewell Observatory today. A copy of Stanford's press announcement is attached."

:-(

Stanford has a lame press release on their web site.

BTW great 5-minute speed talk at Techdirt Greenhouse.

[Mark Bracewell]

Thanks Andy, for the post. The site spawned an amazing array of ideas as well as dishes, it lives on...