Part 1 looked at the difficult, costly, and lengthy journey from concept to a successful launch. Part 2 looked at the severe problems of the HST discovered after launch, and Part 3 looked at what has been learned from the Hubble “experience.” The final installment of this story looks at the plans for a post-Hubble space-based telescope.

The Hubble telescope was supposed to be retired around 2015 (the date has been pushed back several times), but it has been extended due to delays with its successor, the James Webb Space Telescope (JWST), now scheduled for launch in 2021 (also greatly delayed and way over budget!). Hubble was originally supposed to have a 15-year operating life, but it has now passed twenty years since the lens fix and still going.

Hubble may be used into the 2020s (assuming there are no significant component failures). Its usefulness may end before that, of course, since there is no Space Shuttle available for ongoing repairs and maintenance. There was a proposed plan to use some sort of ground-controlled robot system to do maintenance, but on second review, that plan was canceled to technical challenges, risks, costs, and timeline.

The successor JWST features a larger 6.5-meter (21 ft) diameter primary mirror, made in segments as a gold-coated beryllium reflector. Compared to the Hubble’s 2.5-meter mirror, it will have a collecting area about five times as large (25 m² vs. 4.5 m²). It was “unfurled” in April 2016 for initial tests, and you can be sure they will be triple-checked (Figure 1).

There will be no opportunity for repair, upgrade, or even planned basic maintenance for the JWST, and that’s not because the Space Shuttle (or an equivalent) is unavailable. The reason is that the JWST will not orbit Earth but instead will be located near the Earth-Sun L2 Lagrangian “parking” point about 1.5 million kilometers from Earth (Figure 2). (A Lagrange point is a location in space where the combined gravitational forces of two large bodies – such as Earth and the sun, or Earth and the moon – equal the centrifugal force felt by a much smaller third body; the result is the third body appears “stationary” with respect the larger ones.) A large sun shield will keep its mirror and four science instruments below 50 K (−220 °C/−370 °F), so random thermal motion does not interfere with the sensitive readings.

The project was initially funded in 1996 with contributors, including the European Space Agency and the Canadian Space Agency. JWST is designed for a useful life of between five and ten years. The first realistic budget estimates were that the observatory would cost $1.6 billion and launch in 2011. The project was killed by Congress, but funding was later restored, with a budget now at around $10 billion and a planned 2021 launch. In August 2019, engineers successfully connected the two halves of the James Webb Space Telescope for the first time at Northrop Grumman’s facilities in Redondo Beach, California – another major milestone. Looking back and ahead, it appears that while technology certainly advances, but history repeats itself – at least with respect to their technical challenges, budgets, and schedules.

 

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 Other Related Content and References:

Hubble Space Telescope:

• Robert Zimmerman, “The universe in a mirror: the saga of the Hubble Telescope and the visionaries who built it”
• NASA: ST-161, Endeavor and First Hubble Space Telescope Servicing Mission
• NASA: The Hubble Space Telescope Servicing Mission
• NASA: A Brief History of the Hubble Space Telescope
• Astronomy Magazine, NASA extends Hubble Space Telescope science operations contract, June 24, 2016
• CNET News, Overachieving Hubble mission gets five more years, June 26, 2016
• Physics Today, Saving Hubble: A conversation with the director, June 12, 2012

Corona Spy Satellite Program

Dwayne A. Day, John. Logsdon, & Brian Latell, “Eye in the Sky: The Story of the Corona Spy Satellites”

James Webb Space Telescope:

• www.jwst.nasa.gov
• Photonics, JWST’s Giant Golden Mirror is Unveiled, April 28, 2016

Lagrange Points:

• Lagrange Points: Parking Places in Space

Books on Major NASA Projects:

• (about Mars Rovers Spirit and Opportunity, 2004) Steven W. Squyres, “Roving Mars: spirit, opportunity, and the exploration of the red planet”
• (about Voyager 1 and 2, 1977) Stephen J. Pyne, “Voyager: seeking newer worlds in the third great age of discovery”
• (about the Mars Rover, 2012) Adam Steltzner, with co-writer William Patrick, “The Right Kind of Crazy”
• (about the Apollo Moon Mission) Charles Murray and Catherine Bly Cox, “Apollo: The Race to the Moon”