Space travel in Delft all started with shifting stars

In the 1970s and 1980s, Delft researchers were involved in the first Astronomical Netherlands Satellite (ANS). Was this prompted by the 1969 moon landing?

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According to emeritus professors Karel Wakker and Boudewijn Ambrosius, the established order of influential Dutch astronomers considered manned space travel to be a wasteful and pointless activity. At the time, the consensus was that the Netherlands shouldn’t dwell on the issue.

Wakker and Ambrosius are two of the instigators of space activities carried out in the current Faculty of Aerospace Engineering. When Apollo 11 landed on the moon, on 20 July 1969, Wakker had graduated two years previously from the then department of Aeronautical Engineering, and Ambrosius was a second-year student there. As a student, he wasn’t overly motivated because he wasn’t really interested in aircraft constructions or air currents. He came to Delft to study space travel, but it wasn’t until later in the degree programme that this subject was covered in Professor Wittenberg’s performance theory course.

Increasing heartbeat
In the 1960s, guys like Wakker and Ambrosius cut out articles on space travel and wrote to NASA and the Russian Space Agency (the security service even visited the Wakker family asking about their frequent correspondence with Russia). They studied the starry sky and had a telescope to make their own observations. They both told the story about how they suddenly saw an unknown star moving between the familiar stars. It had to be a satellite. Their hearts began to beat faster. Can you also determine how fast, and therefore how high, that satellite is moving? Can you also calculate when it will return? These kinds of questions inspired the small club that had gathered around Professor Wittenberg in Delft.

Wakker and Ambrosius speak the name Wittenberg with an amount of respect that borders on awe. To them, Wittenberg is an underestimated pioneer, someone who had good relationships within Dutch space research and Estec (located in Delft until 1969), and who preferred to give others the opportunity to develop rather than step into the limelight himself.

Orbital mechanics has become a specialty with researchers participating at an international level

“He wasn’t driven by the need for recognition,” says Wakker. For example, when Wakker joined Wittenberg as an engineering assistant after his graduation, he gave him the opportunity to work at Estec in Noordwijk one day a week. Wittenberg let his employees devote all their time to what they loved doing: thrust calculations and orbital mechanics. The book Rocket Propulsion & Space Flight Dynamics, written by Karel Wakker, Koos Cornelisse and Herman Schöyer, was published in 1979. 

Orbital mechanics, or how a satellite or a spaceship moves through space, has become a specialty in Delft with researchers participating at an international level. Astrodynamics is the basis for determining the movement of the Earth’s crust and global sea level, measuring melting land ice or subsidence caused by gas extraction. How did this all happen?

Orbital calculations
One year before the moon landing, Wakker was given a special mission. Wittenberg had connections in the group that wanted to build and launch the first Astronomical Netherlands Satellite (ANS). The purpose of the space telescope was to observe X-ray and ultraviolet radiation. Fokker was responsible for satellite construction, Philips supplied the electronics. Wittenberg put himself forward to do the orbital calculations. Wakker still remembers the conversation. “Wakker, you’re going to do the orbital calculations for the ANS.” And there was only one right answer: “Yes, professor.” These calculations were carried out in TH Delft’s computer centre, first using punched tapes and later with piles of punched cards Wakker handed in at the desk. He would then politely ask when the calculation would be done. “That was usually the next morning.” ANS was launched on 29 August 1974 and orbited the earth in an elliptical orbit at an altitude between 266 and 1,176 kilometres. The mission lasted 20 months and was regarded as a success, partly thanks to the discovery of X-ray bursts – which they couldn’t have done from the ground due to the atmosphere’s ability to absorb X-rays.

Shooting satellites
For a second important mission, the orbital calculations had to be much more accurate. Prof. Leen Aardoom of the former Geodesy department wanted to use a laser from Kootwijk, in the Veluwe area, to measure the distance to geodetic satellites. Those satellites were packed with mirrors that would always reflect a light. But you had to know exactly where to aim the laser. For Wakker and Ambrosius it was “a wonderful new problem”. Wakker explains: “We combined observations from different stations to predict the trajectory of the satellite as it passed over the station at Kootwijk over a period of several weeks.” Ambrosius specialised in computer calculations.

Space travel is not a goal in itself, it’s a way to make things possible

At ESA and NASA, orbital calculations from Delft were considered to be true benchmarks. “We were playing in the big leagues,” remembers Wakker. “NASA didn’t pay us, but they did give us support and data from the international laser station network. We were required to submit reports. It was tough. If you didn’t deliver, you’d soon be out the door.” Ambrosius looks back: “When you can calculate an orbit to within one decimetre, you can also accurately determine the local sea level. Then it becomes interesting to measure the sea’s surface level across the globe. Space travel is not a goal in itself, it’s a way to make things possible.”

Back to the moon?
Fifty years after the first moon landing, there is increasing talk about going back. Do we Dutch still think that’s a wasteful activity? Wakker: “The earth is the cradle of mankind, but one day there will be settlements on the moon and on Mars. Concrete can be made using the water at the poles and moon dust. Various groups are working on that.”

Ambrosius sees the moon as an ideal springboard for further destinations. Solar panels can be used to make propellant from the polar ice for space trips to Mars or further afield.

Another reason to return is the radio silence on the other side of the moon. For Dutch radio astronomers, made famous by the antenna network Lofar and the first ever ‘image’ of a black hole (last April), a radio telescope on the other side of the moon would be invaluable. From there, shielded from the noisy Earth, they can listen to the weakest signals from the earliest days of the universe.

Science editor Jos Wassink

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