Hubble’s Successor and the Man it’s Named After

In 2018, NASA is scheduled the launch the James Webb Space Telescope (JWST). The JWST is the successor to the Hubble Space Telescope. The Hubble, upgraded in 2009, is still producing high quality science. However, it has been in operation for 25 years, and like an old car, will begin to break down sooner or (hopefully) later. It is projected that Hubble will fall back to Earth sometime around 2024.

The JWST will be fundamentally different from the Hubble in three ways, its mirror type, location, and the part of the electromagnetic spectrum observed.

The Hubble’s primary mirror is a single piece 2.4 meters (8 feet) in diameter. The mirror is made of ultra low expansion glass that weights 2,400 lbs. This is pretty lightweight; a regular glass mirror the same size would weigh five times as much. The JWST primary mirror will consist of 18 segments with a total weight of 1375 pounds. The total mirror size will be 6.5 meters (21 feet) in diameter.

Why are the JWST mirrors so light?

The mirrors for the JWST, rather than composed of glass, are made of beryllium. This substance (mined in Utah) has a long history of use in the space program, as it is very durable and heat resistant. In fact, the original Mercury program heat shields were made of beryllium. In space, weight is money. Currently, it cost $10,000 to put a pound of payload into orbit. Since the JWST mirror has 7 times the area of the Hubble mirror, a lighter material had to be found.

Beryllium itself is a dull gray color. The mirrors will be coated with gold to reflect the incoming light back to the secondary mirror to be focused into the JWST instrument package.  The choice of gold was not for aesthetic purposes, but rather gold is a good reflector of infrared light and that is key to the JWST mission.  The total amount of gold used is a little over 1 1/2 ounces, worth roughly $2,000, which is a minute fraction of the JWST $8.5 billion budget (about the same price tag for an aircraft carrier).

The final assembly of the primary mirror will take place at the Goddard Space Flight Center in Maryland. The contractor for the assembly is ITT Exelis, which was formally a part of Kodak and is still based in Rochester, NY.

The JWST will launch in 2018 on an Ariane 5 rocket at the ESA launch facility in French Guiana. This is near Devil’s Island, the site of the former penal colony featured in the film Papillon. Its location near the equator provides a competitive advantage over the American launch site at Cape Canaveral. The closer to the equator, the greater the eastward push a rocket receives from the Earth’s rotation. In Florida, the Earth’s rotational speed is 915 mph. At French Guiana, it is 1,030 mph.  That extra 1,000 mph boost allows a launch vehicle to lift more payload into orbit.

Even if the shuttle program were still active, unlike the Hubble, it would not have been used to lift the JWST into space. The Hubble is situated in orbit 350 miles above the Earth. This was the upper end of the shuttle’s range. The JWST will be placed 1,000,000 miles away from Earth at a spot known as the L2 Lagrange point.  What is the L2 point?  Think of the launch of the JWST as a golfer’s drive shot.  The interplay between the Earth and Sun produce gravitational contours as seen below:

Credit: NASA / WMAP Science Team

The gravitational contours are like the greens on a golf course.  The arrows are the direction gravity will pull an object.  The blue areas will cause the satellite to “roll away” from a Lagrange point.  Red arrows will cause the satellite to “roll towards” the desired destination.  Kind of like this shot from the 2012 Masters:

The L2 spot is not entirely stable.  If the JWST moves towards or away from the Earth, its operators will need to make slight adjustments to move it back towards the L2 spot.  Due to this placement, the JWST will not have the servicing missions the Hubble enjoyed. The specifications of the JWST must be made correctly here on Earth before launch.

Why does the JWST need to be so far away from Earth?

The answer lies in the part of the electromagnetic (EM) spectrum the telescope will observe in. Don’t get turned off by the term electromagnetic, as we’ll see below, you will already be familiar with most parts of the EM spectrum.

Credit: NASA

The word radiation tends to be associated with something harmful, and in some cases, it is.  However, radio and light waves are also forms of EM radiation.  What differentiates one form of radiation from another is its wavelength.  Cool objects emit mostly long wavelength, low energy radiation.  Hot objects emit short wavelength, high energy radiation.  The JWST will observe in the infrared.  And this is a result of the objects the JWST is designed to detect.

The JWST will search the most distant regions of the universe.  Due to the expansion of the universe, these objects are receding from us at such a rapid rate, their light is red-shifted all the way into the infrared.  Planets also emit mostly in the infrared as a consequence of their cool (relative to stars) temperatures.    The infrared detectors on the JWST will enable it to study objects in a manner that the Hubble could not.

The L2 location allows the JWST to be shielded from the Earth, Moon, and Sun all at the same time.  This prevents those bright sources of EM radiation from blotting out the faint sources of infrared that the telescope is attempting to collect.

The video below from National Geographic provides a good synopsis of the JWST.

So, who was James Webb? And why did NASA name Hubble’s successor after him?

The short answer is that James Webb was NASA Administrator during the Apollo era. Given that Apollo may very well be NASA’s greatest accomplishment, that alone might be enough to warrant the honor. However, Webb’s guidance during NASA’s formative years was also instrumental in commencing the space agency’s planetary exploration program. To understand this, lets take a look at John Kennedy’s famous “we choose to go to the Moon” speech at Rice University on September 12, 1962.

During that speech, President Kennedy not only provided the rational for the Apollo program, but stated the following:

“Within these last 19 months at least 45 satellites have circled the earth. Some 40 of them were made in the United States of America and they were far more sophisticated and supplied far more knowledge to the people of the world than those of the Soviet Union.

The Mariner spacecraft now on its way to Venus is the most intricate instrument in the history of space science. The accuracy of that shot is comparable to firing a missile from Cape Canaveral and dropping it in this stadium between the 40-yard lines.

Transit satellites are helping our ships at sea to steer a safer course. Tiros satellites have given us unprecedented warnings of hurricanes and storms, and will do the same for forest fires and icebergs.”

It has to be noted here that soaring rhetoric notwithstanding, Kennedy was not exactly a fan of spending money on space exploration. At least not to the extent the Apollo program demanded. Kennedy felt the political goal of beating the Soviet Union to the Moon trumped space sciences.  Nonetheless, you can see the origins of NASA’s planetary & Earth sciences programs along with applications such as GPS in Kennedy’s speech. So how does James Webb fit into all this?

When tapped for the job as NASA administrator, Webb was reluctant to take the position. Part of it was his background as Webb was a lawyer. He was also Director for the Bureau of the Budget and Under Secretary of State during the Truman Administration. Webb initially felt the job of NASA Administrator should go to someone with a science background. However, Vice President Lyndon Johnson, who was also head of the National Space Council, impressed upon Webb during his interview that policy and budgetary expertise was a greater requirement for the job.

That background paid off well when dealing with both Presidents Kennedy and Johnson. As NASA funding increased rapidly during the early 1960’s, there was great pressure to cut space sciences in favor of the Apollo program. Webb’s philosophy on that topic was this; “It’s too important. And so far as I’m concerned, I’m not going to run a program that’s just a one-shot program. If you want me to be the administrator, it’s going to be a balanced program that does the job for the country that I think has got to be done under the policies of the 1958 Act.”

The 1958 Act refers to the law the founded NASA and stipulated a broad range of space activities to be pursued by NASA.  The law can be found here.

During the 1960’s, NASA’s percentage of total federal spending is below:

Credit: Center for Lunar Science and Exploration

NASA has never obtained that level of funding since. Most of it was earmarked to develop and test the expensive Saturn V launch vehicle. And pressure was often applied from the President to Webb to scale back or delay NASA’s science program to meet Apollo’s goal of landing on the Moon before 1970. The video below is a recording of one such meeting between Kennedy and Webb.

Webb’s law background served him well in making the case for a balanced NASA agenda.  Despite pressure of the highest order, Webb was able to guide both Apollo to a successful conclusion and build NASA’s science programs as well.  The latter would include the Mariner program that conducted flybys of Mercury, Venus, and Mars.  Mariner 9 mapped 70% of Mars’ surface and Mariners 11 & 12 eventually became Voyager’s 1 & 2, humanity’s first venture beyond the Solar System.

Quite a legacy for a non-science guy.

This also demonstrates you do not necessarily have to have a science/engineering background to work in the space program.  Take a gander at NASA’s or SpaceX’s career pages and you will find many jobs posted for backgrounds other than science.  As James Webb proved, it takes more than science to study the universe.

*Image at top of post is JWST mirror segment undergoing cryo testing.  Credit:  NASA.

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