The Hubble space telescope: 'It's a terrificcomeback story'Its 25 years since a shuttle first put the giant space telescope into orbit, but theproject initially seemed doomed to fail. How did Nasas team turn things around,going on to capture over a million stunning images of deep space?

Ian SampleThursday 23 April 2015 07.00BST

The moment had come. Scientists led into the room and set up a screen for thegathered crowd to watch. On it was to appear the rst ever image from Hubble, Nasaspowerful, sparkling space telescope. That, at least, was the plan. Plenty of theastronomers wanted this event called, in the business, rst light to be held awayfrom the media gaze. But the press had been invited and arrived in numbers.Together they waited. And then it arrived: the rst picture of the heavens from themost impressive space telescope ever built, one that promised a revolution in ourunderstanding of the universe.

It was May 1990 and the $1.5bn Hubble had been in orbit for a month. In the room atNasas Goddard Space Flight Centre in Maryland, everyone stared at the image.

Some eyebrows went up, says David Leckrone, a senior scientist who worked onHubble from 1976 until his retirement in 2009. It was supposed to be a picture of abinary star, a pair of stars. But it was just sort of a fuzzy blur. Someone piped up: ItsOK, isnt it? Thats how its supposed to look? Those in the know drew breath. Thatwas not how it was supposed to look.

This Friday, it will be 25 years since the space shuttle Discovery lifted the 11-tonnetelescope into space. The size of a bus, Hubble began circling Earth as TimBerners-Lee wrote the rst page of the World Wide Web, and the England footballteam were preparing for the World Cup in Italy. After a near- disastrous start, Hubblecame to dene our view of the cosmos.

Hubble was named after Edwin Hubble, the US astronomer who discovered in the1920s that the universe is expanding. Much of the science that the telescope did builton his work. But its origins can be traced back to the German scientist HermannOberth who enthused about blasting telescopes into space. It was Lyman Spitzer, aPrinceton astrophysicist, who made the proposal convincing. High above thedistorting blanket of Earths atmosphere, a space telescope could perform science farbeyond the reach of ground telescopes, he argued. His ideas appeared in a 1969report. Lyman was an extraordinary intellect. He won the backing of fellow scientists,

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and ultimately the US Congress.Leckrone joined the US space agency the year that Pitzers report came out, andmoved to the edgling Hubble project seven years later. The telescope was designedto t inside the payload bay of Nasas new eet of space shuttles. Astronauts woulddrop the telescope into orbit, then y back on occasional service missions, using theshuttles robotic arm to grab hold of the telescope and retrieve it.

Nasa hoped to launch Hubble in 1983, but the schedule slipped. The team was aboutready in 1986 when Nasa suered one of the greatest blows in its history. On 28January that year, the space shuttle Challenger disintegrated over the Atlantic Ocean,killing its crew of seven. The disaster grounded the shuttle eet for the best part ofthree years. Without the shuttle, Hubble could not y. The engineers made use of thedelay. When Hubble nally reached the launchpad, seven years late, condence washigh.

Steven Hawley, a former astronaut and astronomy professor at Kansas University,operated the shuttles robotic arm that put Hubble in orbit. When the crew was aboutto start the procedure, he thought of all of the people who had devoted much of theircareers to the dream of a large telescope in space. Everyone was dependent on usexecuting that last step properly, says Hawley. The deployment went well. Hubbleoated free and the shuttle backed away. Onboard, astronauts captured somebreathtaking footage: the telescope apparently suspended as the Earth rolledbeneath.

Nasa engineers spent several weeks checking out Hubbles systems before taking theirrst picture. The image was a huge disappointment, but Leckrone stayed optimistic.They could adjust Hubble in countless ways from Earth. A few weeks work and theywould have it working properly, he thought. Then, some weeks went by and nothingwe did made the image much better. Suddenly the mood became very morose, hesays.

The lowest point came one afternoon at Goddard. The various technical teams hadgathered for their regular status meeting. One by one, they stood up and gave verbalupdates: the computer people, the thermal team, the power group. Then it was timefor the optics team. They were still trying to get good images, but so far had gotnowhere. Then another voice broke in from the back of the room. It was ChrisBurrows, an optics specialist. There was an edge of anger in his voice, saysLeckrone. He said: Youve got half a wave of spherical aberration and there isnothing you can do about it. The room fell silent.

Hubbles 2.4m primary mirror was the product of exquisite workmanship, but thecurvature of the mirror was not quite right around the edges. The fault meant thatimages from the mirror would always be blurred because light rays bouncing o thesurface were not properly focused. None of the adjustments that could be made fromEarth could correct the problem.

The Hubble project was managed by Nasas Marshall Space Flight Centre inHuntsville, Alabama. Some Marshall scientists had heard Burrows speak that

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afternoon. After the meeting, they gathered in a small oce to take stock. AsLeckrone walked in he heard Jean Olivier, Hubbles chief engineer, in downbeatmood. Break out the hemlock, boys, Olivier said.

The situation was bleak, but not as hopeless as Olivier had feared. An optics specialistcalled John Trauger at Nasas Jet Propulsion Lab in California had shown Hubblesrst blurry image to Marjorie and Aden Meinel, a married couple who ranked amongthe worlds best telescope designers. They happened to be on sabbatical at JPL andknocked on Traugers door when they heard Hubbles rst images had arrived. It tookAden a matter of minutes to diagnose spherical aberration.

Some weeks later, Trauger was at a meeting of the Optical Society when he bumpedinto Aden Meinel in the buet queue. They got chatting. Almost in passing, Meineldelivered a bombshell. He knew how to x the problem.

Trauger was building a copy of Hubbles Wide Field and Planetary Camera, as abackup. Inside the camera were a series of coin-sized mirrors that reected light fromHubbles primary mirror into the cameras detector. Meinel worked out that curvingeach of those small mirrors in precisely the right way would cancel out the distortionof the primary mirror.

The space shuttle ew its rst service mission to Hubble in 1993. The crew replacedthe telescopes main camera with Traugers modied version, and tted a seconddevice to correct Hubbles other scientic instruments. Back on Earth, the teampointed the telescope at a patch of space strewn with stars and waited for pictures.

When the rst image came down, it was extraordinarily beautiful, says Leckrone.From that point on, every place we pointed Hubble in the sky, there was somethingnew and remarkable. Its a terric comeback story.

Astronauts repaired the orbiting observatory on ve separate missions. Stabilisinggyros broke, solar panels and a power unit were replaced, and new instrumentsadded. With every mission, we tried to extend Hubbles lifetime and increase itsscientic productivity, says Mike Weiss, former programme director. The lastservicing mission was in 2009, but without the shuttle, no more are planned. Nasascalculation is that Hubbles instruments will pack up in a year or two. At some point,it will be brought down. Most of it will burn up in the atmosphere, but parts will raindown into the Pacic.

Hubble has taken more than a million pictures. It has revealed regions of space wherenewborn stars are surrounded by at discs of dust, the building material for planets ofother solar systems. Its images reveal thousands of galaxies. The faintest light we seeleft those galaxies when the universe was a mere 500m years into its 13.8bn-yearexistence.

Though Hubble is nearing the end of its life, its pictures and raw data will keepscientists busy. Hubble has provided the last couple of generations withawe-inspiring images and tonnes of scientic data, and its going to continueproviding that for decades to come, says Weiss. It has far exceeded our

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TopicsHubble space telescopeSpaceNasaThe space shuttle

expectations. Its been the thrill of a lifetime.

Hubbles big brotherHubble should not fall from the sky until its successor is in orbit. Nasas James WebbSpace Telescope (JWST) is earmarked for launch in 2018, seven years later thanoriginally planned. The telescope will blast o aboard an Ariane 5 rocket from theEuropean spaceport near Kourou in French Guiana. Its nal destination lies about amillion miles from Earth, in the opposite direction to the sun.

Named after Nasas chief administrator during the Apollo programme, the JWST has aprimary mirror more than ve times larger than Hubbles. The mirror is made up from18 hexagonal panels which fold up for launch. Once deployed in orbit, the hugemirror should allow the JWST to see much fainter objects than Hubble.

A giant sunshield the size of a tennis court separates the JWST into two sections. Thewarm, sun-facing side carries solar panels to provide power for the telescopesinstruments. The side facing away from the sun is kept cool, and operates at atemperature of -220C.

Unlike Hubble, the JWST is an infra-red observatory. That gives the telescope theability to look further back in time than Hubble. Because the expansion of theuniverse is accelerating, ancient galaxies are hurtling away from us at enormousspeed. As they recede, the light they emit is stretched to longer wavelengths, makingthem appear more red, or redshifted. By making observations in the infra-red, theJWST will search for the most far-ung objects: the rst stars and galaxies thatformed after the big bang.

Planet-hunting telescopes have spotted about 2,000 candidate worlds beyond oursolar system. The JWST will watch some of these planets as they cross the faces oftheir stars. Light coming from the planets, or through their atmospheres, can revealchanges in seasons on the ground, weather patterns and potentially even signs ofvegetation.

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