The launch of the James Webb Space Telescope on Christmas Day triggered a memory that twenty years ago, in July 2001, I was an invited speaker at a Conference in Cape Town entitled The Early Universe and Cosmological Observations: a Critical Review. That meeting was preceded by the 16th International Conference on General Relativity and Gravitation in Durban which I also attended, but did not speak at. For the Cape Town meeting I was asked to give a talk about some of the things coming up in the future to do with observational extragalactic astronomy, though I was told to avoid the cosmic microwave background and galaxy redshift surveys as other speakers were covering those areas. At the time I was serving on the Astronomy Advisory Panel for the (now defunct) Particle Physics and Astronomy Research Council so I was keeping up with developments fairly well then.
Anyway, I wrote up my talk and it was published in 2002 in a special issue of Classical and Quantum Gravity, along with the other talks (which were more theoretical, as opposed to hypothetical). I never bothered to put in on the arXiv so if you want a copy you’ll have to get it from the publisher.
I’m not claiming it is a particularly insightful article – and I did refrain from giving specific timescales – but, looking back at it, it is interesting which projects I mentioned in the abstract actually did get completed in the following twenty years.
The European X-ray mission XEUS was never completed. It was proposed for a while to merge it with a rival US mission Constellation-X in the International X-ray Observatory (IXO), but that was cancelled in 2011/12 owing to budget constraints at NASA. An ESA X-ray mission, called ATHENA (Advanced Telescope for High ENergy Astrophysics, based to some extent on the XEUS concept, is pencilled in for launch in 2034.
At the time of writing the article, JWST was called the Next Generation Space Telescope (NGST) and was envisaged to be an 8m class telescope, though I did suggest in the article would probably be “de-scoped” to involve a smaller mirror “perhaps 6m or thereabouts”. As we now know, it was finally launched on December 25 2021 and has a mirror of diameter 6.5m.
GAIA was developed and launched in 2013 and will operate until next year; it has been a tremendous success.
The Overwhelming Large (OWL) Telescope was planned to be a huge ground-based telescope, with a 100m diameter mirror and a target timescale of around 2015, to be built by the European Southern Observatory in Chile. I remember in informal discussions we used to call it the FLT. It was eventually decided that was not technically feasible and it was downgraded to a merely Extremely Large Telescope, which has a 39m mirror, underwhelming in comparison. Construction is in progress and it should see first light in 2027.
As well as the ELT there are now also the Thirty Metre Telescope and the Giant Magellan Telescope, which will come into operation on a similar timescale.
The Atacama Large Millimetre Array (ALMA) consisting of 66 telescopes working as an interferometer was completed and has been fully operational since 2013. That too has been a great success.
The Square Kilometre Array (SKA) also had its share of cost overruns and technical delays and although initial construction plans have been developed it is not expected to be operational until 2027.
Probably the most notable omission from my list is the Large Synoptic Survey Telescope (LSST) now called the Vera Rubin Observatory. That wasn’t really within my horizon in 2001, although its planning phase had started then. It really got under way around 2008 and is now nearing completion. I certainly would have mentioned it had I known more about it at the time!
P.S. In case you’re wondering, the Euclid Mission due to be launched in early 2023 was very far from the drawing board in 2001 so I don’t apologize for not mentioning it!
In the Dark 