UniPress: The Bernese Solar Wind Sail

When Buzz Aldrin became the second man to step out of the lunar module on July 21, 1969, the first thing he did was unfurl the Bernese solar wind sail and plant it in the moon's surface, even before the American flag. How did this Solar Wind Composition Experiment (SWC), which was planned and evaluated by Professor Johannes Geiss at the Physics Institute of the University of Bern, end up on the moon?

The Soviet Union, which has an impressive tradition of rocket construction, succeeded in sending the first satellite into Earth orbit in 1957 (Sputnik 1) and in carrying out the first manned space flight in 1961 (Yuri Gagarin). The USA was deeply affected – people spoke of a "Sputnik shock." This led President John F. Kennedy to proclaim shortly after taking office in 1961 that an American would set foot on the moon before the end of the decade. This marked the start of the Apollo program by the American space agency NASA. With Apollo 11, humans actually landed on the moon for the first time on July 20, 1969. When Neil Armstrong and Edwin "Buzz" Aldrin stepped out of the lunar module, it was already July 21, 1969 in Europe.

In 1971, Johannes Geiss tests the functioning of the solar wind sail modified for Apollo 16 in the Contraves climate chamber in Zurich. © University of Bern
Astronaut Edwin "Buzz" Aldrin on the moon with the solar wind sail from the University of Bern, 1969 © NASA

Bern gets involved

The University of Bern also played a part in this first moon landing with its now famous solar wind experiment: shortly after the lunar module touched down, a sheet of aluminum foil was stretched out on the surface of the moon and exposed to the sun. For a certain period of time, this foil captured particles from the solar wind (the composition of the collected solar wind atoms was later analyzed in the laboratories of the Physics Institute in Bern). The experiment was later continued until Apollo 16, but was not included in the last moon landing. The University of Bern was ultimately involved in a total of six Apollo missions (although Apollo 13 did not land on the moon because an oxygen tank exploded during the flight – rescuing the astronauts took priority).

How did this collaboration with the Bernese come about? Years before the first moon landing, scientists began to make proposals for scientific experiments for the planned moon flight. After thorough consultation, the Bernese physicists Johannes Geiss, Peter Eberhardt, and Peter Signer (who was working in the US at the time and later became a professor at ETH Zurich) proposed the solar wind experiment.

Ions and electrons continuously stream out of the sun into space at speeds of over 1 million km/h. This solar wind does not reach Earth because it is slowed down and deflected by the atmosphere and magnetosphere. Unadulterated results about the solar wind can only be obtained in free space or on a celestial body that, like the moon, has virtually no atmosphere. (Johannes Geiss, 1998)

In the fall of 1965, NASA experts, including astronaut Don Lind, came to Bern to take a closer look at the Bern experiment proposal.

In the meantime, preliminary work and tests, in which the then students Fritz Bühler and Jürg Meister proved their worth, were in full swing. However, important questions still needed to be answered: How could the "solar wind sail" be set up on the moon? Could the solar wind even reach the moon's surface? With the limited knowledge at the time about the density of the moon's atmosphere or the strength of its magnetic field, it was not possible to answer this question conclusively. (Johannes Geiss, 1998)

The decision

The year 1967 proved decisive: Geiss attended a NASA meeting in California, where the future landing sites on the moon were selected and the astronauts' excursions and scientific activities were specified in detail. At this meeting, the Swiss “solar wind sail” was included in the program as a whole. The Bernese proposal to participate in the investigation of moon rocks, and in particular to carry out age determinations and other isotope investigations, was also accepted. However, at this meeting, there was no guarantee that the Bernese solar wind experiment would be used on the first moon landing – this decision was not made until the end of 1968. Johannes Geiss was spending nine months in Houston at the time as part of a sabbatical. He was able to watch as astronauts Neil Armstrong and Edwin “Buzz” Aldrin practiced the moon landing program on Earth until all the maneuvers became automatic: They practiced getting in and out, moving in zero gravity, working in the spacecraft and later in the lunar module, setting up the “solar wind sail,” collecting moon rocks, and sleeping.

Every move had to be simulated in order to draw up a realistic schedule. As with pilot training, great importance is attached to responding correctly to incidents and breakdowns. (Johannes Geiss, 1998)

On the old film reel in the archives of the Physics Institute, someone has written by hand: "Astronaut with foil in stormy wind – funny." The NASA footage from May 1968 has now been digitized for the first time. Hans Balsiger, professor emeritus at the University of Bern, worked at Rice University in Houston during the Apollo program and comments on the archive treasure: Astronaut Don L. Lind trains in setting up and dismantling the solar wind sail.

 

Well, the moon landing was a success. Prof. Johannes Geiss was also at NASA's control center in Houston during the first moon landing. No sooner had the two astronauts, Armstrong and Aldrin, set foot on the moon than the solar wind sail was erected. This happened even before the American flag had been hoisted.

In order to collect solar wind particles for as long as possible, our experiment had to be set up as early as possible, which meant that the solar wind sail was competing with the American flag. Together with NASA scientists on site in Houston, we managed to ensure that our experiment was given very high priority in the sequence of astronaut activities on the moon. In the end, the Bern experiment was allocated 70 minutes. The first excursion on the moon lasted only two and a half hours in total. (Johannes Geiss, 1998)

The successful solar wind experiment made the Bernese physicists incredibly popular at the time: there was hardly a magazine or TV station that did not report on it. The Swiss solar wind experiment was not only a media success, but also a complete scientific triumph.

The results concerning the isotopic composition of noble gases are still used today in the field of solar physics and in questions concerning the formation of planets, astrophysics, and even cosmology. The scientific objectives have been fully achieved. (Johannes Geiss, 1998)

While the solar wind sail was used to study the sun and its development over time, most of the other Apollo experiments and analyses of moon samples were used for lunar research. The University of Bern also made important contributions to this field.

The solar wind measurements taken during the Apollo missions marked the beginning of a highly successful research program at the University of Bern involving satellite-based exploration of the sun using ESA and NASA space probes, which is still ongoing today. Instruments from the University of Bern were carried aboard missions such as ISEE-3, Ulysses, WIND, SOHO, ACE, Genesis, and Solar Orbiter.

* This article is an abridged and updated version of an article published in UniPress No. 96 in April 1998 (original in German).

The quoted passages were inserted by Prof. Geiss himself in 1998.

Johannes Geiss, pioneer of space research

Johannes Geiss played an important role in the establishment and development of European space research for decades. Born on September 4, 1926, in Pomerania, Geiss studied physics in Göttingen and earned his doctorate in experimental physics in 1953. Between 1953 and 1958, he was a research assistant at the universities of Chicago and Bern, and in 1957 he qualified as a professor in Bern. After holding a professorship in ocean sciences at the University of Miami, he was elected associate professor in Bern in 1960 and appointed full professor in 1964. Following the death of Professor Friedrich Georg Houtermans in 1966, Geiss served as director of the Physics Institute at the University of Bern until two years before his own retirement in the fall of 1991. From 1995 to 2002, Johannes Geiss was co-director of the International Space Science Institute (ISSI) in Bern, which was founded on the initiative of scientists from four Swiss universities and representatives from Swiss industry and the federal government.