NASA, National Aeronautics and Space Administration
The mesosphere/lower thermosphere (MLT) lies between the turbulent mixing and diffusive layers of the earth’s upper atmosphere. Temperatures in this region are varied and include the coldest region of the earth’s atmosphere, the mesopause. Too high for aircraft and too low for satellites, the only method of direct access to the MLT is by sounding rocket for periods of at most a few minutes. Because of this, the MLT is the most difficult region of the earth’s atmosphere to access and is therefore the least understood region of the earth’s atmosphere. Accurate in-situ measurements of MLT species are important for the following reasons:
•CO2 concentration profiles collected in-situ will be useful in validating and improving atmospheric temperature measurements made by satellite based instruments, for example, the Sounding of the Atmosphere using Broadband Emission Radiometry on the TIMED spacecraft.
• Study the transport of atmospheric species near the turbopause region. For example, NO, which is thought to be linked to ozone depletion in the stratosphere
• In-situ concentration data will help to improve atmospheric models, such as the MSIS model
We present an axially-sampling time-of-flight mass spectrometer (TOF-MS) suitable for deployment aboard sounding rockets to make measurements in the MLT. Use of a Bradbury- Nielsen gate to modulate ions makes on-axis sampling possible. The TOF-MS also employs a pressure tolerant microchannel plate (MCP) detector capable of operating at pressures into the 10-4 torr range. We have built and are currently testing a prototype instrument in our ion optics facility. Experiments to date demonstrate the potential of the TOF-MS to successfully make measurements in the MLT and thereby improve our knowledge of this important region of the earth’s atmosphere.
Available at: http://works.bepress.com/addison-everett/5/