New York’s Goddard Space Science Center is a singularly unromantic place. But, on a summer day in 1974, this bleak office block in upper Manhattan was the venue for a meeting with more than just a little romance about it. The seven men who came together that day were proposing nothing less than a quest for the Holy Grail of cosmology.
The catalyst was John Mather, a tall, lean young astronomer barely six months out of graduate school. Before moving east to New York he had cut his cosmological teeth on balloon experiments with Paul Richards at Berkeley. What had prompted him to arrange the meeting at Goddard was Announcement of Opportunity AO6&7, a request by NASA for proposals for new space missions.
‘It was obvious to everyone that a satellite would have enormous advantages for probing the microwave background,’ says Dave Wilkinson, one of the seven astronomers at the meeting. Not only would the instruments on board be able to peek at the Universe from above the weather, but they would be relentless, sitting in orbit for months on end, soaking up the precious photons of background radiation. ‘A satellite would well and truly nail the problem,’ says Wilkinson.
Over the next few months, Mather’s team, which included Wilkinson and Ray Weiss of MIT, hammered out a proposal for a satellite that would carry four separate experiments into Earth orbit. The experiments would include one to measure the spectrum of the Big Bang radiation better than anyone had ever dreamed, and another to scan the whole microwave sky, searching for the tiniest departure from absolute smoothness.
‘I was only 28 years old at the time we put in the proposal, so I can’t say I really took it seriously,’ says Mather. ‘But I knew one thing: the idea behind the experiment was a good one.’
NASA was deluged with hundreds of space proposals, but Mather’s team was in luck. Already, several of NASA’s own science committees had identified a space experiment to observe the birth of the Universe as just the sort of project the agency ought to be carrying out. Such experiments were impossible from the ground and could be done only from space. They were also of fundamental importance to science, dealing with nothing less than the origin of the Universe in the most gigantic explosion of all time.
NASA was also shrewd enough to realise that such a project was likely to capture the imagination of the public. ‘Everyone wants to know how we got to be here,’ says Mather. ‘And that was precisely the question we aimed to answer.’
But unknown to Mather and his team, others had also set their sights on the Big Bang. Among the sackloads of space proposals delivered to NASA headquarters were two others for putting a satellite in orbit to probe the faint afterglow of creation. One came from a team led by Samuel Gulkis of the Jet Propulsion Laboratory in Pasadena, California; the other was from Luis Alvarez and his colleagues at the University of California at Berkeley.
Alvarez was a legendary physicist: a Nobel Prize-winner who during the war had worked on both the development of the atomic bomb and of radar. In a remarkably diverse career he had carried out a search for undiscovered chambers inside Chephren’s pyramid using natural X-rays from space, and started his own company to make variable focus contact lenses.1
That a scientist of the calibre of Alvarez had zeroed in on a measurement of the Big Bang radiation only served to underline how important it was to science.
Both Alvarez and Gulkis wanted to look for tiny departures from smoothness in the microwave background – a single element of Mather’s more ambitious proposal. ‘It was immediately clear we overlapped,’ says Mather.
NASA, forced to choose between rival cosmic background proposals, came up with a neat solution. It formed a study team with investigators chosen from each of the three proposals.
At this point, Alvarez decided to drop out. The project was now more ambitious than the one he had originally envisaged and, at 65, he had a strong suspicion that he might not last the duration.2 In his place he nominated a young Berkeley researcher named George Smoot.
Smoot was destined to become the team’s most controversial figure.
The satellite, by now christened the Cosmic Background Explorer (COBE) and essentially Mather’s proposal, would take three experiments high above the troublesome atmosphere. It would protect them from the light and heat from both the Sun and the Earth, supply them with electrical power and transmit their data back down to the ground.
One instrument – the Far Infrared Absolute Spectrophotometer (FIRAS), a direct descendant of experiments Mather had flown on balloons while at Berkeley – would determine the spectrum of the Big Bang radiation a hundred times better than ever before to see whether it really was a black body.
A second instrument – the Diffuse Infrared Background Experiment (DIRBE) – would search for the infrared glow of the first galaxies to form out of the cooling gas of the Big Bang.
The third instrument – the Differential Microwave Radiometer (DMR) – was descended from instruments flown by George Smoot and Phil Lubin, and by Dave Wilkinson. It would map the brightness of cosmic microwave background with extraordinary sensitivity, looking for the slightest signs of any unevenness.
In 1976, NASA selected the Goddard Space Flight Center as the focal point for further studies. For the next decade and a half, this sprawling facility at Greenbelt on the outskirts of Washington DC would be the headquarters for the COBE effort. The people working there would make the greatest day-to-day contribution to the project.
In 1982, after a series of feasibility studies, NASA finally gave the team the go-ahead to start building COBE. The launch was eventually set for 1989.
Selecting an orbit for COBE was no mean feat. The sensitive instruments would have to be kept out of the Sun as much as possible, and during the course of a year they would have to see the whole sky.
The Goddard engineers picked a ‘polar’ orbit which would swing the satellite round from pole to pole and always keep it flying along the boundary between night and day. The orbit would gradually drift, so the instruments would eventually see all the sky.
The engineers also had to find a way to control the satellite’s orientation as it raced through space. If its sensitive instruments ever pointed anywhere near the Sun or the Earth, they would be completely blinded. The ‘attitude control system’ that ensured this never happened was such a tour de force of Goddard engineering that the team came to dub it the ‘fourth experiment’.
Once it was decided that COBE should be put into a polar orbit, the launcher for the satellite was dictated. NASA had a very reliable expendable launcher called a Delta rocket which was just the job. ‘Everything in the experiment called out for a Delta launch,’ says Wilkinson.
But NASA had other ideas. By the 1980s, the agency had plumped firmly for the reusable space shuttle as the workhorse of its space effort. ‘It had put all its eggs in the shuttle basket,’ says Charles Bennett, a researcher who joined the COBE team in 1984. Despite objections from the team, NASA insisted on launching COBE on the space shuttle. ‘The agency simply didn’t want competition from throwaway launchers,’ says Wilkinson.
At the time, the shuttle was being launched from Cape Canaveral, at the tip of Florida, from where it was impossible to put a payload into a polar orbit. But NASA pointed out that it was planning to build a second launch site for the shuttle at Vandenberg Air Force Base in the desert of southern California. From Vandenberg it would be possible to launch a satellite into a polar orbit.
Being scheduled to take off from a launch facility that was still on the drawing board was a serious worry for the team. But NASA had spoken and it was footing the $60-million bill for the project. Mather’s team knuckled down and began redesigning COBE for launch on the space shuttle.
The changes to the satellite were not trivial at all. ‘When NASA forced us onto the shuttle, it was a major trauma,’ says Wilkinson. For one thing, the satellite now needed to have a rocket strapped to it to boost it from the shuttle’s cargo bay into its orbit. The shuttle could haul itself to a height of only 300 kilometres above the Earth, but COBE’s polar orbit was 900 kilometres up.
A shuttle launch brought other worries, too. For instance, gases in the shuttle’s cargo bay might contaminate the satellite, and unwanted radiation from them could swamp the faint hiss from the cosmic background. But there was a much needed boost to the morale of the team in January 1983 when NASA successfully launched its Infrared Astronomical Satellite. ‘IRAS was before us in the queue, so you can imagine, we were very keen to see that satellite go,’ says Mather.
But there was another reason for wanting to see IRAS succeed. In common with COBE, it carried a giant vacuum flask of liquid helium to cool down its instruments so that they would be more sensitive. Liquid helium, which boils at only 4.2 degrees above absolute zero (–269°C), is not the easiest substance to handle at the best of times. ‘Nobody had used liquid helium in space before,’ says Mather, ‘so people were terrified the technology would not work.’
However, the IRAS satellite was a great success, relaying back stunning pictures of some of the coldest objects in the Universe – newborn stars and great curtains of gas and dust hanging across space. ‘The liquid-helium technology passed its most severe test,’ says Mather. ‘We all breathed a great sigh of relief.’
By 1986, COBE was largely built. But, on 28 January, the space shuttle Challenger exploded into a thousand flaming pieces in the blue Florida sky, killing all seven astronauts on board. As the horrific pictures of the accident were flashed around the television screens of the world, the COBE project seemed to be in ruins. Not only did NASA put all its space projects on indefinite hold, but the agency shelved, then abandoned completely, its plans to build the second launch site out in California. ‘It was a traumatic time for everyone,’ says Wilkinson. ‘The engineering staff at Goddard had already built most of the COBE hardware.’
But the team’s hopes were not entirely dashed. After Challenger, the US government made a decision to get things moving again as quickly as possible and demonstrate that NASA was still capable of launching satellites successfully.
‘There was a whole list of satellite projects waiting to go,’ says Bennett. ‘Everyone wanted to see their experiments launched.’
The task facing NASA was a formidable one. ‘It had a limited budget,’ says Bennett. ‘It had all these projects. And it had some terrible decisions to make. Like, what projects do we delay indefinitely? And what ones do we cut out entirely?’
The COBE team went to work looking at alternative launch vehicles. ‘It was abundantly clear to us that if we didn’t get the satellite off the shuttle, it would never be launched,’ says Bennett. The team considered hitching a ride on the French Ariane rocket. They even considered talking to the Russians. ‘Back then, that wasn’t nearly as easy to suggest as it is today,’ says Bennett.
But, finally, they came back to their original choice – the trusty Delta rocket. It was ironic: after originally designing COBE for a Delta launch and then redesigning it for launch by the shuttle, the team began redesigning it for a Delta launch once again. It was enough to make anyone despair.
By the end of 1986, Mather and the team had formulated a new plan. It involved halving the weight of the satellite and making all sorts of things on the spacecraft fold up so it would squeeze into the shroud on top of a Delta rocket. ‘We went to NASA headquarters and said we could rebuild COBE and launch on a Delta in a short time,’ says Bennett. ‘Of course, lots of other projects were coming in saying the exactly same thing. It was a mad scramble.’
Getting the weight down was the biggest challenge facing the COBE team. ‘We had a 10,500-pound spacecraft designed for the shuttle, and the Delta rocket couldn’t launch more than 5,000 pounds!’ says Bennett.
That it was possible to readapt COBE at all for a Delta launch was something of a miracle. ‘Fortunately for us, NASA chose COBE as its number-one priority, along with the Hubble Space Telescope,’ says Bennett. ‘The agency considered the science solid and genuinely exciting. The buzzword was that it was “sexy”, and sure to capture the public’s imagination. The other thing was that they believed we could do it soon.’
At the beginning of 1987, NASA gave COBE the green light, on one condition – that the satellite be ready to go in two years. ‘Two years is not a lot of time to redesign, rebuild and retest a spacecraft,’ says Bennett.
The COBE team was elated. The only doubt was whether all the changes to the satellite could be made in time. ‘The Goddard engineers did a sensational job of converting the satellite,’ says Wilkinson. ‘Without them, COBE would have died.’
The satellite’s own propulsion system was no longer needed to boost the satellite from the shuttle’s cargo bay. It could be dispensed with immediately. ‘That took 2,000 pounds off at a stroke,’ says Bennett.
But getting the rest of the weight off was a major problem. Luckily, the giant 600-litre vacuum flask that contained the liquid helium and the three sensitive instruments could just squeeze into the shroud of the Delta. And the boxes containing all the electronics still fitted. But the entire spacecraft skeleton had to be completely remade.
Someone had a bright idea and realised that the old spacecraft structure – basically a large piece of metal for bolting things onto – might come in useful somewhere else. It was sold to another project that was planning to use the shuttle.
Some things now had to be built folded up, ready to open up in space. For instance, COBE needed an upside-down umbrella hanging beneath it to hold back the torrent of heat, radar and television streaming up from the Earth. This ‘ground shield’ had to be deployable in orbit. But using such a ‘deployable’ in space is a very risky business. ‘If it doesn’t open, you’ve had it,’ says Bennett. ‘You just can’t go up into space and fix it.’
For two and a half years, rebuilding the satellite was a major activity at Goddard. Engineers and technicians worked double shifts and weekends to convert the spacecraft, and the lights out at Greenbelt often burned late into the night. ‘Everyone felt a great sense of pride in the project,’ says Bennett.
Though only about 50 people followed the project from beginning to end, more than 1,000 contributed in some way to COBE. ‘You need to decide what kind of glue to stick this bit to that bit,’ says Bennett. ‘Well, some guy is an expert on glue, so he plays a part.’
The attention paid to the minutest detail of COBE was phenomenal. ‘I’ll never forget this meeting we had that lasted for two hours,’ remembers Bennett. ‘We were discussing a bolt – a single bolt. How long should it be? How many turns per inch? What way should it turn?
‘Before I worked on COBE, I always thought people who built space experiments spent too much time worrying about ridiculous details. But the rocket cost $60 million. You can’t go and launch n of those, where n is a large number. These things are incredibly complicated. It really is a wonder anything works.’
Of crucial importance to the experiment was the cold load. It was this that would be compared with the sky to find out how close it was to a black body. The team ended up with a blackened cone, which they strapped to a metal plate, bolted in turn to the vacuum flask of liquid helium.
A critical factor that contributed to COBE’s success was that the engineers and scientists on the project talked to each other a lot. Some of the scientists, including Mather and Bennett, were at Goddard the whole time, making day-to-day decisions along with the engineers. ‘The COBE project was small enough that this sort of interaction was possible,’ says Bennett. ‘On big space projects, scientists only write a “requirements document”, hand it to the engineers, and the engineers go away and build the spacecraft.’3
Another thing that helped COBE was the dedication of scientists like Mather and Bennett. By working on the project to the exclusion of almost all else, they freed others, like Dave Wilkinson, to continue working on their own experiments. Wilkinson and the rest were therefore able to keep at the forefront of a fast-moving field while learning more and more about the pitfalls of doing cosmic background experiments. ‘We were constantly updating our experience,’ says Wilkinson. ‘And COBE was able to take advantage of that.’
There were always things the experimenters had not anticipated which swamped the tiny signal from the cosmic background radiation. On one occasion, Wilkinson and a graduate student flew a balloon in which a tiny metal switch scuppered the entire experiment. As the balloon drifted on the winds, the switch cut through the Earth’s magnetic field, inducing a spurious electrical current. COBE’s switches were magnetically shielded to avoid the problem.
For Wilkinson, the balloon experiments were a breath of fresh air after the frustrations and compromises of COBE. He could be in ‘complete control’. ‘Dave kept himself aloof from daily involvement in COBE,’ says Mather. ‘He came to our meetings several times a year and helped think about what we should do, but he did not try to do it.’ For people like Mather, however, who were deeply involved, COBE was a constant effort.
When everything was built, it was time to test it. The equipment had to be able to survive not only the rigours of launch, but also the harsh environment of space.
Rocket launches are incredibly violent events. Putting a payload on a rocket is rather like placing a bomb under it. Delta rockets have ‘accelerometers’ at different points, so engineers know exactly how each part of the rocket shakes during launch.
At Goddard there is a building with a table which can shake equipment just as if it were on a real rocket. ‘You have to watch through a thick window,’ says Bennett. ‘You can’t be in the same room – the noise would destroy your ears.’
The team built fake instruments and bolted them to the test table. They shook the table, but harder than necessary – just to be sure. When nothing dropped off, they put the real instrument on the table and started praying. ‘It’s a scary thing to watch,’ says Bennett. ‘You work on these incredibly delicate instruments and then you shake the hell out of them.’
The instruments passed their test. It was time to shake the entire spacecraft. Some of the people on the team could hardly watch. They stood around horror-struck, biting their lips, convinced something would go wrong. ‘You wouldn’t believe anything would work after being shaken like that,’ says Bennett. ‘If you shook your TV set like that, it would be a pile of junk.’
COBE passed with flying colours. ‘The shake test was a big thing,’ says Bennett. ‘The redesigned spacecraft was particularly vulnerable to vibration because it was lighter than we originally planned.’
The second big test was the thermal test, which took place in Goddard’s Solar Environmental Simulator. The spacecraft was put in a vacuum chamber to mimic space and something hot and bright was shone on it to simulate the Sun. The instruments had not only to survive this baking, but also work well.
The thermal test lasted a whole month. ‘It was a month when a lot of us didn’t get much sleep,’ recalls Bennett. Ahead of time, he had drawn up the schedule of tests on the smoothness experiment. It was necessary, for instance, to check how well the satellite’s batteries worked and whether its attitude-control system functioned as expected.
The COBE team zipped through the test schedule, but occasionally someone would get a result they did not understand, so they would need more time. Bennett was forced to revise the schedule constantly. ‘You don’t go back in once you come out of the Solar Environmental Simulator,’ says Bennett. ‘So you have to do your analysis quickly … I can’t explain how much this business wears you down. Afterwards, you feel utterly drained.’
Another thing that had to be done was to make sure COBE’s instruments were not ‘talking to each other’. The satellite had to have a radio transmitter on board in order to transmit data back down to the Earth. ‘We had these extraordinarily sensitive instruments and a several-watt transmitter sitting right in the middle!’ says Wilkinson. But none of the transmitter power seemed to leak into the instruments. All was okay.
COBE eventually passed all of its tests with no problems. But the gods had not finished with the nerves of the COBE team. Several months before the planned launch, the team hit problems. The mechanical arm which brought the cold load in and out of the FIRAS spectrometer’s trumpet-shaped horn would not stay in place.
The giant vacuum flask was already filled with super-cool liquid helium. Nevertheless, there was nothing for it but to take the lid off, take the cold load out, install a new flexible electrical cable, put it back together and cool it all down again. ‘It cost us several months,’ says Mather.
Finally, after two and a half years of non-stop activity, everything was ready. COBE had taken a mammoth 1,600 person-years to build and it had cost a total of $60 million.
Folded up, the satellite was drum-shaped, about six feet in diameter and 12 feet tall. In space, with its solar panels completely unfurled, it would span about 20 feet.
The launch was set for 18 November 1989. The night before, most of the team flew out to Vandenberg Air Force Base, 100 miles north of Los Angeles. ‘They got us up at 3 a.m. or some ungodly hour like that and put us onto buses,’ says Bennett. ‘It was freezing. I remember trying to get warm on the bus.’
When the buses put them down in a field about a mile from the launch pad, dawn was still some time away. ‘The launch wasn’t scheduled for an hour, but they’d got us there early,’ says Bennett. ‘Of course, there was no guarantee the launch would not be delayed.’
It was a large gathering in the field, and there was great excitement. Dave Wilkinson was there. He had been in at the very beginning. He was the only experimenter to span the entire history of the cosmic background measurements. Standing beside him was his ‘secret weapon’. ‘I think my dad was the only one sad to see COBE come along,’ says Wilkinson. ‘It meant we stopped our balloon campaigns, so he could no longer come and help.’
Also waiting in the crowd, stamping their feet to keep warm, were Ralph Alpher and Robert Herman. Mather had made a special point of inviting them. Now, everyone recognised their prescience in predicting the Big Bang radiation back in 1948.
‘That was the most nervous time of all,’ says Bennett. ‘Waiting for the launch.’ Delta rockets are just about the most successful of all launch vehicles, but even they fail occasionally. ‘Years of our lives had gone into this thing,’ he says. ‘It really was all or nothing.’
‘We had our fingers crossed and crossed again,’ says Wilkinson. ‘There were so many things that could go wrong. There were 600 litres of liquid helium on that satellite. It had to get into a high and difficult orbit. It had to be oriented, spun up. The cover had to come off, the ground shield had to pop out …’
Dawn was breaking when an extraordinarily bright light flared low in the clear sky. Bennett drew in a sharp breath. He had expected to hear a loud sound first. ‘My first thought was, “Oh no, it’s blown up!”’ But everything was okay. ‘I suppose the people who see lots of these things know it’s quite normal.’
To the relief of everyone, the blinding light began to climb steadily into the sky. After 15 years of effort, COBE was at last on its way. ‘Seeing it streaking across the sky – that was a beautiful sight,’ says Bennett.
He did not wait around. As the rocket faded into invisibility, he dashed to a car. ‘I had to get back to Goddard,’ he says. ‘I was the one responsible for getting the smoothness experiment turned on and checked out.’
Bennett sped through the desert. ‘It was funny. I was driving to Los Angeles and I was hearing news reports on the car radio about how COBE was doing. It was my main source of information. The radio reported a successful launch. Then, the golden age of cosmology just before I arrived at the airport, I heard there had been a successful orbit injection, and that the solar panels were working.’
From a payphone at the airport Bennett called Goddard. When he got through to the control room, they told him everything was working well. COBE had reached its orbit 900 kilometres above the Earth. It was now circling the Earth 14 times a day, a tiny, drifting star, brightening and fading every 72 seconds as it turned on its axis. It could be seen in the night sky, going from south to north a little after sunset, or from north to south a little before dawn.
COBE awakened, opening its eyes to the microwave Universe.
1. In 1980, Alvarez would hit newspaper headlines all over the world by claiming to have found evidence that a giant impacting asteroid wiped out the dinosaurs 65 million years ago.
2. Alvarez was right. He died in 1988, a year before the launch of COBE.
3. This may have contributed to the problems of the much bigger Hubble Space Telescope which was launched into orbit in 1988 with the telescopic equivalent of a squint.