The U.S. Naval Research Laboratory (NRL) successfully launched two experiments on the SpaceX Falcon 9 rocket to the International Space Station (ISS) from the Kennedy Space Center (KSC), as part of a commercial resupply mission on Feb 19.
The experiments are the Limb-Imaging Ionospheric and Thermospheric Extreme Ultraviolet (UV) Spectrograph (LITES) and the Global Positioning System (GPS) Radio Occultation and UV Photometer Co-located (GROUP-C) experiments, lead by Drs. Andrew Stephan and Scott Budzien, research physicists at NRL.
Using high-sensitivity UV photometry and GPS radio occultation, Budzien’s GROUP-C remotely observes vertical and horizontal structures in the ionosphere. GROUP-C uses remote sensing in the orbit plane to characterize the low and mid-altitude ionosphere, specifically two-dimensional structures at night.
According to Budzien, the instruments used in GROUP-C are second-generation power sensors designed to improve performance, while reducing overall size and weight. Earlier versions of the NRL photometer flew aboard a U.S.—Taiwan six-satellite mission known as the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC), also called FORMOSAT-3. The GROUP-C experiment builds upon the joint UV-GPS measurement technique successfully demonstrated during that mission.
“The instrument suite includes state-of-the-art hardware designed to demonstrate high-performance, low-cost, compact space sensors suitable for future space environment and space weather satellite missions,” said Budzien.
A new and important capability of LITES experiments, stated by Stephan, is its continuous observation of the entire altitude range, and capturing a series of structural images in the upper atmosphere and ionosphere. Unlike past sensors that sample one altitude at a time with a scanning mirror, LITES uses a compact optical imaging design to improve the ability to see changes on shorter timescales, with better sensitivity.
Stephan says LITES underwent significant alterations in its hardware to meet its research goals from the ISS platform. These modifications improved the precision of ionospheric measurements during the day, complementing GROUP-C’s ability to measure at night.
“This sensor has its heritage back to my days as a graduate student, and it is fulfilling to see it contribute to the mission of the NRL-Space Science Division and to provide, via our collaboration with the University of Massachusetts Lowell, an opportunity to work with the next generation of space scientists as they gain experience conducting these cutting-edge experiments with us,” said Stephan.
Stephan and Budzien affirm that GROUP-C and LITES have “unprecedented” remote sensing aptitudes in combination with one another.
Both scientists emphasize that GROUP-C and LITES form a suite of high performance sensors, that function day or night, producing two-dimensional and three-dimensional maps that display multi-scale plasma structures found in the ionosphere. The presence of these plasma structures causes scintillation, the term given to random fluctuations in GPS and other radio waves that propagate through this region, which degrade performance and add noise to Navy operational systems.
“Locating and measuring these structures in the ionosphere will ultimately be useful to Navy and DoD forecasts, and specify the high frequency signal propagation environment relevant to communication, geolocation, and radar applications,” said Budzien.
Preparation for the project began July 2014, with the payload expected to collect data for at least two-years after its launch. If the experiment’s equipment is maintained aboard the ISS, Budzien and Stephan hope to continue operating the experiments and collecting data beyond the designated timeframe.