sounding the sun
July 13, 2014

Sounding Rocket Set To Study The Sun’s Energy

April Flowers for - Your Universe Online

On July 14, NASA will launch a sounding rocket from White Sands Missile Range in New Mexico. A little before noon, the rocket will streak 180 miles into the atmosphere, sending it into the thermosphere layer, beyond the ozone's ability to block the sun's high energy light.

Sounding rockets are small payload, scientific research rockets. Named for the nautical term "to sound," which means to take measurements, the rockets have been flying for NASA-sponsored space and earth research since 1959. There are 15 types of sounding rockets, which range in size from the Super Arcas at 7 feet to the Black-Brant XII at 65 feet. Sounding rockets are used so often because they are simple, cost-effective and time efficient. The payload experiments can be developed in approximately six months and many of the fuel motors are military surplus.

Monday's launch will spend six minutes observing the extreme ultraviolet and soft X-rays streaming from the sun, using the new Degradation Free Spectrometers. These instruments will measure the sun's irradiance, or the total energy output in these short wavelengths.

In conjunction with the sun's approximately 11 year solar cycle, scientists know that the total solar irradiance, and especially the irradiance at high energy wavelengths, changes over time. Researchers are less certain of how these changes occur over longer periods of time. This information is important, however, in understanding how Earth's space environment is affected by solar variability.

"Data observations from recent missions have provided significantly improved measurements of irradiance," Leonid Didkovsky, principal investigator for the mission at the University of Southern California in Los Angeles (UCLA), said in a recent NASA statement. "But the optical components of many of these missions can degrade during the time of the mission. Degradation leads to calibration drift over time."

The scientific instruments aboard sounding rockets take a lot of effort to compare and calibrate from Earth. Traditionally, they require expensive technologies and sometimes, additional rocket flights to track changes in the instrument as it ages. Didkovsky and his colleagues recently developed degradation-free instruments to do away with the need for in-flight calibration. The launch on the 14th will carry two of the new instruments (the Optics-Free Spectrometer and the Dual Grating Spectrometer), and two traditional instruments.

The Optics-Free Spectrometer uses neon gas to detect photons from the sun. As solar photons collide with neon, electrons are emitted. The number of electrons emissions and the energy are measured. The data gained from this instrument could be used to characterize the original light striking the detector.

Visible light can be separated from the extreme ultraviolet light by the Dual Grating Spectrometer, using two very stable, degradation-free versions of a diffraction transmission grating tool. The US National Institute of Standards and Technology calibrated both of the new instruments at its Synchrotron Ultraviolet Radiation Facility.

The two traditional, or classic, instruments will be the Rare Gas Ionization Cell absolute irradiance detector and the Solar EUV Monitor. The Solar EUV Monitor is a clone of an instrument aboard the ESA / NASA Solar and Heliospheric Observatory.

"The mission will do more than simply gather irradiance data during the flight," said Didkovsky. "One of the important goals is to demonstrate that these two degradation-free instruments are flight-ready."

A Terrier-Black Brant MK3 rocket will carry the Degradation Free Spectrometers experiment, with a window for launch that begins at 3:10 EDT.

Image 2 (below): The Degradation Free Spectrometers experiment will measure the total energy of the extreme ultraviolet light coming from the sun, to better understand how it changes over time – which has implications for understanding solar evolution. Credit: NASA


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