Stratospheric Flight of Three Mars Surface Instrument Prototypes

The Analog Site Testbed for Readiness Advancement (ASTRA) is a high-altitude balloon platform for the testing of Mars surface instrument systems. In September 2012 three prototype instruments, a mass spectrometer and two anemometers, were taken to the 6 mbar pressure level of Earth's stratosphere (~34.5 km) above New Mexico to demonstrate their current capabilities and identify the critical path-to-flight steps for future advancement. Each of the instrument systems deployed on ASTRA were rated at TRL 4 at the start of the project. Through laboratory development, environmental testing, and the ASTRA balloon flight, each has advanced to an overall system TRL of 5, with specific subsystems reaching TRL 6. The results from the Rapid Acquisition Mass Spectrometer (RAMS), the Hot-Wire Anemometer (HWA), and the Single-Axis Sonic Anemometer (SASA) from the mid-September flight are presented, with focus given to both scientific results of the terrestrial atmospheric investigations, and the engineering and technical performance of the individual instrument systems and the balloon platform. The RAMS instrument has unique ion-imaging optics which permit the acquisition of a complete mass spectrum in a single CCD frame (~50 ms minimum). This allows RAMS to see rapid fluctuations in atmospheric constituents (necessary for the study of, for instance, vapor fluxes to and from the Mars surface) and has potential applications for laser ablation mass spectroscopy. The HWA is the latest generation of hot-wire anemometer, with heritage from the Mars Pathfinder MET instrument, and the ATMIS sensors developed for the Mars Polar Lander and the NetLander project. In addition to wind speed, a thermocouple cage around the hot filament detects heat plume direction, thus permitting 2-D wind vectors to be established. The SASA is a proof-of-capability device for an eventual three-axis sonic anemometer design. Developed under PIDDP funding by Dr. Don Banfield of Cornell (thus a contributed instrument to ASTRA), the SASA uses novel ultrasonic transducers capable of acoustic coupling to the thin Mars atmosphere. Rapid resolution of wind vectors (order 20 Hz), eventual 3-D capability, an open sensing volume, and high sensitivity, accuracy, and precision (order 2 cm/s) make this technique attractive for the measurement of turbulent eddies in the planetary boundary layer.