The Ram Energy Distribution Detector (REDD) is a new CubeSat-compatible space science instrument that measures neutral wind characteristics in the upper atmosphere. Neutral gas interactions with plasma in the ionosphere/thermosphere are responsible for spacecraft drag, radio frequency disturbances such as scintillation, and other geophysical phenomena. REDD is designed to collect in-situ measurements within this region of the atmosphere where in-flight data collection using spacecraft has proven particularly challenging due to both the atmospheric density and the dominating presence of highly reactive atomic oxygen (AO). NASA Marshall Space Flight Center has a unique AO Facility (AOF) capable of simulating the conditions the sensor will encounter on orbit by creating a supersonic neutral beam of AO. Collimating the beam requires an intense magnetic field that creates significant interference for sensitive electronic devices. REDD is undergoing the final stages of validation testing in the AOF. In this presentation, we describe the LabVIEW-automated system design, the measured geometry and magnitude of the field and the specially designed mount and passive shielding that are utilized to mitigate the effects of the magnetic interference. / Master of Science / The Ram Energy Distribution Detector (REDD) is a new CubeSat-compatible space science instrument that measures winds in near-Earth space. Gas interactions with plasma in the upper regions of the atmosphere are responsible for spacecraft drag, radio wave disturbances, and other phenomena. REDD is designed to collect direct measurements within this region of the atmosphere where in-flight data collection using conventional spacecraft has proven particularly challenging. The environmental testing needed to demonstrate the sensor requires a specialized system located at NASA Marshall Space Flight Center. To simulate the conditions the sensor will encounter on orbit within a laboratory requires exposing REDD to a supersonic beam of gas using NASA’s unique Atomic Oxygen Facility. Forming this gas into a beam requires an intense magnetic field that creates significant interference for sensors such as REDD. Testing in this facility requires a specially-designed sensor mount and magnetic shielding system. REDD is undergoing the final stages of validation testing in the Atomic Oxygen Facility. In this presentation, we describe the computer software-automated system for testing the sensor, the shape and strength of the magnetic field, the specially designed sensor mount, and magnetic shielding that are used to mitigate the effects of the interference.

In-situ composition measurements of the mesosphere/lower thermosphere (MLT) are challenging; this region is only accessible via high-speed sounding rockets, ambient pressures extend into the 10-3 Torr range, and particles of interest range in mass from electrons to meteoric smoke and dust particles. Time-of-flight mass spectrometers (TOF-MS) are capable of making fast, accurate measurements over a wide mass range. However, since they rely on pressure-sensitive microchannel plate (MCP) detectors and high voltages, they have rarely been applied at these altitudes. A new TOF-MS for making in-situ composition measurements in the MLT has been developed at the Space Dynamics Laboratory. This instrument employs modest acceleration potentials and a pressure-tolerant MCP detector. A Bradbury-Nielsen gate is used to produce short, well-defined ion pulses to reduce the temporal and spatial uncertainty of sampled ions. A prototype TOF-MS was constructed and used to demonstrate TOF-MS technology under conditions relevant to in-situ MLT measurements. Operational boundaries and capabilities of this new instrument were identified through laboratory experiments combined with computer modeling. The prototype instrument achieved a maximum resolution of 100 at m/z 40 (Ar), sufficient to resolve major atmospheric species of interest. During experiments at elevated pressures, the MCP detector maintained low background count rates (/second) at pressures as high as 10-3 Torr. A novel getter-based vacuum system was evaluated for use with the new TOF-MS, and a computer model was developed to simulate instrument pressure during a rocket flight. Results from these experiments suggest that when combined with an appropriately sized sampling aperture, this pumping system can extend the measurement range of the instrument to lower altitudes by 10 – 20 km, compared to an unpumped instrument. A computer model was developed to study the effects of critical operating parameters on instrument performance; the most important factor affecting resolution was found to be the initial energy spread of sampled ions. Sensitivity and number density measurement analyses suggest the new instrument will measure major species in the MLT at better than 10% uncertainty. Composition measurements made with the new TOF-MS will contribute to a better understanding of the MLT.