
Boeing 747SP Telescope Plane: How the Starship Enterprise Was Landed Forever
The flying laboratory is a joint project of the German and American space agencies (DLR, NASA). Its operation began in 2010. After 12 years, an agreement was signed to end the flights, the maintenance of which cost 85 million dollars per year.
Both space agencies agreed with the recommendations of the National Council of the US Academy of Sciences. It is the body that determines what research will receive budget money in the next decade. There had been talk of shutting down the project since 2014, but the stratospheric observatory had been experiencing financial difficulties at the time. Nevertheless, the project, which is being carried out on by plane, released in 1977, was closed on 29.09.2022/XNUMX/XNUMX.
The first question that arises is: why is this necessary? There are ground-based telescopes, as well as orbital ones (Hubble). However, with the help of the former, it is possible to study only a specific celestial sector, and in a strictly defined period of time. But the main advantage of a telescope on board an airliner is that it flies above the huge mass of water vapor that rises from the troposphere and absorbs infrared radiation.
The starry sky is best seen at night. Photo: youtube.com
As for the orbital telescope, to study a specific area of the sky, the machine has to be moved. And doing this in space conditions is not at all easy. With the help of an aircraft observatory, it becomes possible to photograph the desired part of the sky at any time.
For example, in 2011, the Pluto eclipse could only be observed from an airplane: at that time, in the only observatory on Earth that allowed the rare phenomenon to be captured. The onboard laboratory can also be called a "backup option" in case the orbital telescope fails.
The observatory on board the aircraft is not affected by space debris.
In 1965, astronomer J. Kuiper decided to observe Venus in the infrared range for the first time from a narrow-body Convair CV-990. Three years later, US physicist F. Lowe studied Jupiter with his twelve-inch telescope mounted on a Learjet. Convinced of the promise of such research, in 1969 NASA began developing the KAO project, which stands for "Kuiper Airborne Observatory" (named after the pioneer). To implement the idea, they used the C-141 aircraft, which housed a 36-inch (91,44 cm) telescope.
The first flying observatory on the Convair CV-990. Photo: youtube.com
Thanks to KAO, the rings around Uranus were discovered and the atmosphere of Pluto was studied. The service life of the flying laboratory came to an end in 1995. But already in 1984, NASA published a project to equip a Boeing 747 with a telescope 3 m in diameter. The Germans joined the idea, promising to finance 20% of the costs. The agreement was signed in 1996. The project was called "Sophia".
Observations of celestial bodies were conducted from a height of 13 km: the resulting image was close in quality to a photo from an orbital telescope.
This is the Boeing 747SP, a shortened version of the 747-200 passenger jet. The model was introduced in 1973. In addition to a smaller body, the aircraft received lightweight wings and simplified mechanization for them. A 20-ton weight reduction with the same four engines allowed the Boeing to fly higher and at a higher speed.
Standard passenger Boeing. Photo: VK Video
This was exactly the kind of machine that was best suited for the SOFIA mission. At an altitude of 13 km, the liner bypasses 99% of rising water vapor. The plane with the number N747NA has been used as a regular passenger since 1977.
Shortened version – Boeing 747SP. Photo: VK Video
In 1986 it was resold to another airline, and in 1995 it was put into storage. In 1997, the aircraft was de-preserved and acquired by NASA. The following year, the aircraft began to be converted into a "flying telescope".
Conversion of an aircraft into a flying observatory. Photo: VK Video
First of all, they installed a bulky door that could be closed (opened) right during the flight. Behind it is a 2,5 m diameter mirror telescope, as well as counterweights and stabilizers that give the device stability during observations.
Telescope plane inside. Photo: VK Video
The cabin was re-equipped so that scientists could work in flight. The aircraft first took to the skies for research in 2010. It was then able to photograph the cores of the M82 galaxy and Jupiter.
This is a 2,7 m diameter mirror that collects light and focuses it. The reflective surface, made of aluminum, is carefully polished and concave.
Telescope in the making. Photo: VK Video
The light beam hits the main mirror, then the front edge of the telescope, and finally the focal plane, where the recording device is located.
The mirror is based on a glass ceramic composite called Zerodur. It is interesting because it has zero thermal expansion. Another reflector is made of silicon carbide. It took several months to polish the mirrors!
The list can be very long: during the existence of the flying observatory, thousands of scientists climbed on board. And each of them discovered something new. We will limit ourselves to the most significant studies.
In the cockpit. Photo: VK Video
In 2015, the atomic oxygen content on Mars was measured. This allowed us to understand that the planet is quite “friendly” to underground microbes. That same year, the onboard telescope was able to study planets outside the solar system. Initially, it was believed that the SOFIA project was not capable of this.
Comets have also been found to contain water similar to Earth's. Pluto's atmosphere has been found to be much stronger than previously thought. In 2020, water molecules were reported to exist on the Earth-facing side of the Moon.
Financial troubles accompanied the project from the very beginning. A year before the first flight, the allocated amount increased from the estimated 185 to 330 million "greenbacks". During the first 5 years of research, almost 614 million were spent instead of the planned 265 million dollars. Then the "snowball" only grew. The first time the flying observatory was almost closed in 2014: the Americans demanded that the Germans increase funding.
The plane with the telescope has become very expensive. Photo: VK Video
For example, it turned out that an hour of flight cost $100. But US legislators supported the project and by 2015 the money was allocated. The head of the SOFIA mission even said that the observatory would operate until 2014. However, "the thunder still struck": in 2020, Donald Trump presented a budget project that did not provide money for SOFIA. The following year, the National Council of the Academy of Sciences recommended that NASA abandon further use of the flying laboratory.
The reason for the cooling of interest in the project was also voiced: it was stated that the level of scientific research was incommensurate with the amount of funding. In short, more could have been done for this money. Other programs were cited as an example, which demonstrated a high level of research with similar funding. Despite protests from American and German scientists, the project was closed.
The Last Flight. Photo: youtube.com
In 2022, the aircraft made 144 flights, taking to the skies for the last time on September 28. The flying observatory was sent to the Arizona Aviation Museum. The unique equipment is going to be used for other research. But it is possible that it will be left in the museum.
Both space agencies agreed with the recommendations of the National Council of the US Academy of Sciences. It is the body that determines what research will receive budget money in the next decade. There had been talk of shutting down the project since 2014, but the stratospheric observatory had been experiencing financial difficulties at the time. Nevertheless, the project, which is being carried out on by plane, released in 1977, was closed on 29.09.2022/XNUMX/XNUMX.
Why do people explore space from airplanes?
The first question that arises is: why is this necessary? There are ground-based telescopes, as well as orbital ones (Hubble). However, with the help of the former, it is possible to study only a specific celestial sector, and in a strictly defined period of time. But the main advantage of a telescope on board an airliner is that it flies above the huge mass of water vapor that rises from the troposphere and absorbs infrared radiation.

As for the orbital telescope, to study a specific area of the sky, the machine has to be moved. And doing this in space conditions is not at all easy. With the help of an aircraft observatory, it becomes possible to photograph the desired part of the sky at any time.
For example, in 2011, the Pluto eclipse could only be observed from an airplane: at that time, in the only observatory on Earth that allowed the rare phenomenon to be captured. The onboard laboratory can also be called a "backup option" in case the orbital telescope fails.
In 2009, a piece of an exploded Chinese satellite, which had reached the end of its operational life, flew past Hubble at a distance of 3 km.
The observatory on board the aircraft is not affected by space debris.
Pioneers of Aircraft Observatories
In 1965, astronomer J. Kuiper decided to observe Venus in the infrared range for the first time from a narrow-body Convair CV-990. Three years later, US physicist F. Lowe studied Jupiter with his twelve-inch telescope mounted on a Learjet. Convinced of the promise of such research, in 1969 NASA began developing the KAO project, which stands for "Kuiper Airborne Observatory" (named after the pioneer). To implement the idea, they used the C-141 aircraft, which housed a 36-inch (91,44 cm) telescope.

Thanks to KAO, the rings around Uranus were discovered and the atmosphere of Pluto was studied. The service life of the flying laboratory came to an end in 1995. But already in 1984, NASA published a project to equip a Boeing 747 with a telescope 3 m in diameter. The Germans joined the idea, promising to finance 20% of the costs. The agreement was signed in 1996. The project was called "Sophia".
The flying laboratory has nothing to do with the female name. SOFIA stands for Stratospheric Observatory for Infrared Astronomy.
Observations of celestial bodies were conducted from a height of 13 km: the resulting image was close in quality to a photo from an orbital telescope.
About the SOFIA project aircraft
This is the Boeing 747SP, a shortened version of the 747-200 passenger jet. The model was introduced in 1973. In addition to a smaller body, the aircraft received lightweight wings and simplified mechanization for them. A 20-ton weight reduction with the same four engines allowed the Boeing to fly higher and at a higher speed.

This was exactly the kind of machine that was best suited for the SOFIA mission. At an altitude of 13 km, the liner bypasses 99% of rising water vapor. The plane with the number N747NA has been used as a regular passenger since 1977.

In 1986 it was resold to another airline, and in 1995 it was put into storage. In 1997, the aircraft was de-preserved and acquired by NASA. The following year, the aircraft began to be converted into a "flying telescope".

First of all, they installed a bulky door that could be closed (opened) right during the flight. Behind it is a 2,5 m diameter mirror telescope, as well as counterweights and stabilizers that give the device stability during observations.

The cabin was re-equipped so that scientists could work in flight. The aircraft first took to the skies for research in 2010. It was then able to photograph the cores of the M82 galaxy and Jupiter.
Telescope design
This is a 2,7 m diameter mirror that collects light and focuses it. The reflective surface, made of aluminum, is carefully polished and concave.

The light beam hits the main mirror, then the front edge of the telescope, and finally the focal plane, where the recording device is located.
In 2015, actress Nichelle Nichols, one of the characters from the series "Star Trek": she played Lieutenant Nyota, boarded the plane with scientists. The heroine of the film said that the flying observatory resembled the spaceship "Enterprise".
The mirror is based on a glass ceramic composite called Zerodur. It is interesting because it has zero thermal expansion. Another reflector is made of silicon carbide. It took several months to polish the mirrors!
Project return
The list can be very long: during the existence of the flying observatory, thousands of scientists climbed on board. And each of them discovered something new. We will limit ourselves to the most significant studies.

In 2015, the atomic oxygen content on Mars was measured. This allowed us to understand that the planet is quite “friendly” to underground microbes. That same year, the onboard telescope was able to study planets outside the solar system. Initially, it was believed that the SOFIA project was not capable of this.
Comets have also been found to contain water similar to Earth's. Pluto's atmosphere has been found to be much stronger than previously thought. In 2020, water molecules were reported to exist on the Earth-facing side of the Moon.
Closing
Financial troubles accompanied the project from the very beginning. A year before the first flight, the allocated amount increased from the estimated 185 to 330 million "greenbacks". During the first 5 years of research, almost 614 million were spent instead of the planned 265 million dollars. Then the "snowball" only grew. The first time the flying observatory was almost closed in 2014: the Americans demanded that the Germans increase funding.

For example, it turned out that an hour of flight cost $100. But US legislators supported the project and by 2015 the money was allocated. The head of the SOFIA mission even said that the observatory would operate until 2014. However, "the thunder still struck": in 2020, Donald Trump presented a budget project that did not provide money for SOFIA. The following year, the National Council of the Academy of Sciences recommended that NASA abandon further use of the flying laboratory.
The reason for the cooling of interest in the project was also voiced: it was stated that the level of scientific research was incommensurate with the amount of funding. In short, more could have been done for this money. Other programs were cited as an example, which demonstrated a high level of research with similar funding. Despite protests from American and German scientists, the project was closed.

In 2022, the aircraft made 144 flights, taking to the skies for the last time on September 28. The flying observatory was sent to the Arizona Aviation Museum. The unique equipment is going to be used for other research. But it is possible that it will be left in the museum.
- VK Video, youtube.com
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