ACCENT Microwave Temperature Profiler (MTP)

Instrument: Microwave Temperature Profiler (MTP)

Principal Investigator: Michael J. ("MJ") Mahoney

Organization: Jet Propulsion Laboratory
                         Mail Stop 246-101
                         4800 Oak Grove Drive
                         Pasadena, CA 91109-8099

Phone:             (818)-354-5584
FAX:                (818)-354-4341
E-mail:             Michael.J.Mahoney@jpl.nasa.gov
URL:                http:\\eis.jpl.nasa.gov\mtp\

Prinicple of Operation:
The WB57 MTP is a passive microwave radiometer, which measures the natural thermal emission from oxygen molecules in the earth’s atmosphere for a selection of elevation angles between zenith and nadir. The current observing frequencies are 56.6 and 58.8 GHz, although more may used for the ACCENT flights. The measured "brightness temperature" versus elevation angle is converted to air temperature versus altitude using a linear statistical retrieval procedure. An altitude temperature profile (ATP) is produced in this manner every 16 seconds (about 3 km) along the flight path, and these can be used to produce a color-coded temperature curtain (CTC) of the temperature field which the WB57 has flown through.

The most fundamental use of the MTP is to provide meteorological context for measurements made by in situ and remote sensors of atmospheric gases and aerosols. In arctic regions for example, the ATP can be used to locate altitudes where the air is cold enough to condense nitric acid or water vapor to form polar stratospheric clouds. In addition, the temperature field can used to determine the tropopause altitude, which is extremely important to interpreting other measurements. The ATP can also be used to derive the altitudes of isentrope surfaces to look for the presence of meso- to synoptic-scale atmospheric waves. The "waviness" of isentropic surfaces is used to characterize the magnitude of temperature fluctuations, which is needed for deriving effective temperatures to be used in atmospheric chemistry calculations involving reaction rates and solubility.

Hardware Description:

The MTP on the WB57 consists of three components: the sensor unit (located behind the fairing in the figure above), the data unit (which controls the sensor unit and records data from it), and the real-time analysis computer (which converts the measured brightness temperatures into an altitude temperature profile). The latter two components are located in the pod adapter ring rack. A video feed of the ATP is available for display in the back seat of the WB57 (shown to the right), and this information can be used in real-time to control the altitude of the WB57 with respect to the tropopause. The total mass of the instrument is ~ 15 kg, split roughly equally between the three components.

MTP/WB57 Performance:
Accuracy: Temperature accuracy is approximately 1 K within 3 km of the WB57, and
< 2K for an 8 km region centered on the WB57.
Response Time: Temperature profiles are obtained every 16 seconds.

For more information, go to the MTP Home Page ( http:\\eis.jpl.nasa.gov\mtp\ )