NASA launches Brazilian solar observation telescope
February 24, 2016
By Elton Alisson | Agência FAPESP – The payload of a stratospheric balloon launched on January 19 by NASA, the US National Aeronautics and Space Administration, includes two scientific instruments designed to study the Sun. The balloon was launched from McMurdo, the main US station in Antarctica.
One of these instruments is Solar-T, a double photometric telescope designed and built in Brazil by researchers at Mackenzie Presbyterian University’s Center of Radio Astronomy and Astrophysics (CRAAM) in collaboration with colleagues at the University of Campinas’s Center for Semiconductor Components (CCS-UNICAMP).
Solar-T is coupled to an instrument called GRIPS, short for Gamma-Ray Imager/Polarimeter for Solar flares, designed and built at the University of California, Berkeley, in the US.
Developed with support from FAPESP via a Thematic Project and a regular research grant, Solar-T is the first scientific instrument of its kind built in Brazil, after 15 years of research and development.
Other sources of support for the project besides FAPESP include the following agencies: the Mackenzie Research Fund (MackPesquisa), the National Council for Scientific and Technological Development (CNPq) and the Ministry of Education’s Office for Faculty Development (CAPES) in Brazil; NASA and the Air Force Office of Scientific Research (AFOSR) in the US; and Argentina’s National Scientific & Technological Research Council (CONICET).
“The development of Solar-T represents an opportunity for Brazilian qualification in advanced space technology that could give rise to new satellite projects, for example, and contributions to the International Space Station,” said Pierre Kaufmann, a researcher affiliated with CRAAM and principal investigator for the project.
“We’re collaborating with the Lebedev Institute in Moscow to develop terahertz telescopes for installation on the International Space Station,” Kaufmann told Agência FAPESP. “The success of the Solar-T mission is a necessary condition for us to qualify the technology we’ve developed.”
Together, Solar-T and GRIPS weigh more than three tons. The stratospheric balloon with the instruments on board is flying at an altitude of 40,000 m and will circumnavigate Antarctica for 20-30 days.
While it flies over the frozen continent, Solar-T will capture the energy from solar flares at the highest frequencies ever measured in this kind of observation, between 3 terahertz (THz) and 7 THz, corresponding to a fraction of far-infrared radiation.
Solar flares can be best observed in the terahertz range of the electromagnetic spectrum, which lies between visible light and radio waves. Solar flares are created when magnetic fields in active regions of the Sun suddenly change, hurling jets of accelerated charged particles (electrons and ions) at very high speeds toward Earth.
In the vicinity of our planet, these particles disrupt telecommunications and GPS satellites and also produce auroras around the North and South Poles.
Far-infrared radiation from solar flares can be used in a new approach to the investigation of phenomena that produce energy in active regions located in the three layers of the Sun’s atmosphere: the photosphere, its visible surface, where temperatures do not exceed approximately 5,700 degrees; the chromosphere (20,000 degrees); and the corona (more than 1 million degrees) (read more in Portuguese at http://revistapesquisa.fapesp.br/2015/11/17/na-origem-das-explosoes-solares/).
“These frequencies from 3 THz to 7 THz can’t be measured at ground level because they’re blocked by Earth’s atmosphere. We have to go into space to measure them,” Kaufmann said.
Solar-T measures these frequencies with two photometers (instruments that gauge the intensity of photons), collectors, telemetry, and filters to block undesirable radiation (near-infrared radiation and visible light) that could mask the phenomena of interest and to select frequencies in the 3-7 THz range (read more at http://agencia.fapesp.br/17198/).
Two on-board computers store and compress the data acquired by Solar-T, downlinking these data via the Iridium satellite network to Earth, where they are stored on two computers at CRAMM.
“Transmission of the data acquired by Solar-T to Earth is important to protect us against a loss of the on-board computers. We can’t control where the balloon will eventually land. Antarctica is huge, even bigger than Brazil, and access is difficult,” Kaufmann said.
Solar-T’s photometers, computers and telemetry system are all working normally, he added. Power comes from solar panels coupled to two batteries.
Solar-T was activated on board the stratospheric balloon the day after launch and almost immediately began sending data to Earth.
The solar tracking and pointing system must be accurate to approximately half a degree. This level of precision is assured by GRIPS’s automatic pointing and tracking platform, with which Solar-T is aligned.
“The instruments haven’t yet captured any major solar flares, but if and when they do, we’ll receive the data for analysis,” Kaufmann said.
The stratospheric balloon was successfully launched by a team coordinated out of NASA's Columbia Scientific Balloon Facility (CSBF) in Palestine, Texas, after seven failed launch attempts since December 2015.
The previous attempts failed because of uncooperative weather conditions, especially wind speeds on the ground and in the upper atmosphere, including the stratosphere, which extends to approximately 50 km above Earth’s surface.
The right combination of weather conditions on the ground and in the middle to upper atmosphere is critical, Kaufmann explained. It is also very hard for meteorologists to forecast.
“Launch operations are costly, involving large numbers of people, vehicles and even aircraft, so the margin of risk must be as small as possible,” he said.
“We paid nothing because we were invited to join the mission by the GRIPS team after we presented Solar-T at an international conference. We were looking for a launch vehicle and had even considered developing our own.”
Space experiments like Solar-T cost much less when carried aloft on stratospheric balloons than on satellites, he added.
Science balloons are launched at this time of year for two main reasons: the pattern of stratospheric winds around the South Pole, known as the polar vortex, is favorable, and the Sun never sets during the Antarctic summer, meaning that solar panels can continuously supply power.
“Even now, during the solar cycle’s declining phase, there’s a strong chance we’ll detect a reasonable flare by observing around the clock for 20-30 days while Solar-T is in the stratosphere,” Kaufmann said.
If Solar-T had not been launched now, he added, it would have been a considerable setback. An attempt next year would be unproductive because by then, the solar cycle will have declined further. “And we were coming to the end of Antarctica’s two-month summer window. It would have been very hard to persuade NASA to invest in a new mission,” Kaufmann said.
The flight path of the Mission 668N stratospheric balloon with GRIPS and Solar-T on board can be followed on the CSBF website at www.csbf.nasa.gov/map/balloon8/flight668N.htm.
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