The Far Side

Things become obsolete very quickly these days.  Take the Hubble Telescope for instance. On April 24, 1990, shuttle mission STS-31 saw the  Discovery shuttle launch the telescope successfully into its planned orbit. From its original total cost estimate of about US$400 million, the telescope cost about US$4.7 billion by the time of its launch. Then the real costs started. There was a big problem right off the bat. Hubble had a flawed mirror, researchers learned when the telescope reached orbit and was put to work. It did eventually give us all a view of the Universe we had never been able to have before and boy did it open our eyes. But as ever, we want more.

And it is going to cost even more.

The  James Webb Space Telescope (JWST, or the Webb) may be the most eagerly anticipated of the Super Telescopes. Maybe because it has endured a tortured path on its way to being built. Or maybe because it’s different than the other Super Telescopes, what with it being 1.5 million km (1 million miles) away from Earth once it’s operating.

http://www.universetoday.com/134229/rise-super-telescopes-james-webb-space-telescope/

If you’ve been following the drama behind the Webb, you’ll know that cost overruns almost caused it to be cancelled. That would’ve been a real shame.
The JWST has been brewing since 1996, barely 6 years after Hubble was put in place, but has suffered some bumps along the road. 

Initial estimates for the JWST were a $1.6 billion price tag and a launch date of 2011. But the costs ballooned, and there were other problems. This caused the House of Representatives in the US to move to cancel the project in 2011. 

However, later that same year, US Congress reversed the cancellation. Eventually, the final cost of the Webb 

came to $8.8 billion, 

with a launch date set for October, 2018. That means the JWST’s first light will be much sooner than the other Super Telescopes.

Of the 243 million adults in America, only 122 million pay any taxes. At least as many are freeloaders who do not contribute to the cost of the telescope. But at $73 for all those that do, it is not such a huge amount. Of course if it goes the same inflationary way as the Hubble it could eventually cost the nearly 12 times original budget instead of the current 5.5 times. 

And no doubt Obama will take all the credit for it being there at all.

"I built that"

The JWST will do its observing while in what’s called a halo orbit at L2, a sort of gravitationally neutral point 1.5 million km from Earth.

The Hubble is in Low Earth Orbit, and has a primary mirror of 2.4 meters. The JWST will be located in orbit at the LaGrange 2 point, and its primary mirror will be 6.5 meters. The Hubble observes in the near ultraviolet, visible, and near infrared spectra, while the Webb will observe in long-wavelength (orange-red) visible light, through near-infrared to the mid-infrared. This has some important implications for the science yielded by the Webb.

The James Webb is built around four instruments:
• The Near-Infrared Camera (NIRCam)
• The Near-Infrared Spectrograph (NIRSpec)
• The Mid-Infrared Instrument(MIRI)
• The Fine Guidance Sensor/ Near InfraRed Imager and Slitless Spectrograph (FGS/NIRISS)

The NIRCam is Webb’s primary imager. It will observe the formation of the earliest stars and galaxies, the population of stars in nearby galaxies, Kuiper Belt Objects, and young stars in the Milky Way. NIRCam is equipped with coronagraphs, which block out the light from bright objects in order to observe dimmer objects nearby.

NIRSpec will operate in a range from 0 to 5 microns. Its spectrograph will split the light into a spectrum. The resulting spectrum tells us about an objects, temperature, mass, and chemical composition. NIRSpec will observe 100 objects at once.

MIRI is a camera and a spectrograph. It will see the redshifted light of distant galaxies, newly forming stars, objects in the Kuiper Belt, and faint comets. MIRI’s camera will provide wide-field, broadband imaging that will rank up there with the astonishing images that Hubble has given us a steady diet of. 

The spectrograph will provide physical details of the distant objects it will observe.

The Fine Guidance Sensor part of FGS/NIRISS will give the Webb the precision required to yield high-quality images. NIRISS is a specialized instrument operating in three modes. It will investigate first light detection, exoplanet detection and characterization, and exoplanet transit spectroscopy.

The over-arching goal of the JWST, along with many other telescopes, is to understand the Universe and our origins. The Webb will investigate four broad themes:

• First Light and Re-ionization: In the early stages of the Universe, there was no light. The Universe was opaque. Eventually, as it cooled, photons were able to travel more freely. Then, probably hundreds of millions of years after the Big Bang, the first light sources formed: stars. But we don’t know when, or what types of  stars.

As Genesis tells us, it was a void and God said "Let there be Light". Perhaps they will find God's fingerprints all over it.

• How Galaxies Assemble: We’re accustomed to seeing stunning images of the grand spiral galaxies that exist in the Universe today. But galaxies weren’t always like that. Early galaxies were often small and clumpy. How did they form into the shapes we see today?

• The Birth of Stars and Protoplanetary Systems: The Webb’s keen eye will peer straight through clouds of dust that ‘scopes like the Hubble can’t see through. Those clouds of dust are where stars are forming, and their protoplanetary systems. What we see there will tell us a lot about the formation of our own Solar System, as well as shedding light on many other questions.

• Planets and the Origins of Life: We now know that exoplanets are common. We’ve found thousands of them orbiting all types of stars. But we still know very little about them, like how common atmospheres are, and if the building blocks of life are common.

These are all obviously fascinating topics. But in our current times, one of them stands out among the others: Planets and the Origins of Life.

The recent discovery the TRAPPIST 1 system has people excited about possibly discovering life in another solar system. TRAPPIST 1 has 7 terrestrial planets, and 3 of them are in the habitable zone. It was huge news in February 2017. The buzz is still palpable, and people are eagerly awaiting more news about the system. That’s where the JWST comes in.

One big question around the TRAPPIST system is “Do the planets have atmospheres?” The Webb can help us answer this.

First though we have to do the Launch and Deployment. The science that the JWST will provide is extremely intriguing. But we’re not there yet. There’s still the matter of JWST’s launch, and it’s tricky deployment.

The JWST’s primary mirror is much larger than the Hubble’s. It’s 6.5 meters in diameter, versus 2.4 meters for the Hubble. The Hubble was no problem launching, despite being as large as a school bus. It was placed inside a space shuttle, and deployed by the Canadarm in low earth orbit. That won’t work for the James Webb.

The above image shows the Hubble Space Telescope being held above the shuttle’s cargo bay by the Canadian-built Remote Manipulator System (RMS) arm, or Canadarm. A complex operation, but not as complex as JWST’s deployment

The Webb has to be launched aboard a rocket to be sent on its way to L2, it’s eventual home. And in order to be launched aboard its rocket, it has to fit into a cargo space in the rocket’s nose. That means it has to be folded up.

The mirror, which is made up of 18 segments, is folded into three inside the rocket, and unfolded on its way to L2. The antennae and the solar cells also need to unfold.

Unlike the Hubble, the Webb needs to be kept extremely cool to do its work. It has a cryo-cooler to help with that, but it also has an enormous sunshade. This sunshade is five layers, and very large.

We need all of these components to deploy for the Webb to do its thing. And nothing like this has been tried before.

The Webb’s launch is only 7 months away. That’s really close, considering the project almost got cancelled. There’s a cornucopia of science to be done once it’s working.


But we’re not there yet, and we’ll have to go through the nerve-wracking launch and deployment before we can really get excited.

Of course, if it goes the same way Hubble did, and doesn't work properly, it will be a very long haul for the repair persons to go to fix it. 

There will be lady mechanics, won't there?

I shall pull many a pint twixt now and then.

Pax