Washington, May 20 (IANS): NASA is all set to launch a sounding rocket to help adjust a key instrument aboard NASA's Solar Dynamics Observatory (SDO).

The SDO is studying the solar atmosphere to help scientists understand the Sun's influence on Earth and near-Earth space.

The seventh calibration mission for an instrument on NASA's SDO will launch into space onboard a sounding rocket for a 15-minute flight.

The instrument to be calibrated is called EUV Variability Experiment (EVE) where EUV stands for extreme ultraviolet.

EVE's job is to observe the total energy output of the Sun in EUV light waves.

The calibration mission is scheduled for launch on Thursday on a Terrier-Black Brant suborbital sounding rocket from White Sands Missile Range, New Mexico.

Solar instruments in space naturally degrade over time, bombarded by a constant stream of solar particles that can cause a film of material to adhere to the optics.

Decades of research and engineering skill have improved protecting such optics, but one crucial solution is to regularly recalibrate the instruments to accommodate such changes.

"Parts of the optical coating can darken due to exposure to solar ultraviolet radiation and high energy particles in space, so the sensitivity of the EVE detector decreases over time," said Tom Woods, principal investigator for this calibration mission from University of Colorado in Boulder.

"By determining how much the instrument has degraded since last time, we can adjust data processing algorithms to account for that change," he said.

EVE measures the total energy output of the Sun known as irradiance for each wavelength of light in the extreme ultraviolet range.

By tracking the irradiance, scientists can observe how it changes with different events on the sun.

None of these wavelengths can penetrate the Earth's atmosphere to reach humans on the Earth, but each can have a profound effect on the air above our planet, the US space agency said in a statement.