MicrowaveTemperatureProfiler

Operational Status: Requestable, ready for deployment
General Description:
- MTP is a scanning radiometer that observes emitted radiance (brightness temperature) at 56.363 GHz, 57.612 GHz, 58.363 GHz. It collects measurements at 10 viewing angles between +/- 80 degrees from horizontal. It is housed in a PMS canister with a modified fairing which has a transparent window built into the front. The block diagram below shows the wing-mounted and cabin components of the system (JPL proprietary design).
- A scan mirror is driven by the stepper motor and views at 10 elevation angles from near-nadir to near-zenith. The scan mirror also views a reference target during each scan for gain calibration purposes. The RF signal received by the scan mirror is directed is fed through a feed horn into the radiometer. The frequency synthesizer feeds a microwave signal into the radiometer to down-convert the RF signal. The detected signal is processed by a voltage-to-frequency converter and sent to the controller board which communicates with the cabin computer. The controller board also receives and processes commands from the cabin computer and sends data to the cabin computer where it is processed, displayed, and recorded.
- The wing-mounted sensor and canister:
- The scanning mirror, feed horn, and reference target:
- Scanning Geometry for a hypothetical two-channel MTP:
Measurement Characteristics:
- Overall estimate of uncertainty:
- Uncertainty in the final temperature retrievals varies with distance from flight level. Various sources contribute to the error, including side lobe interference and errors in the statistical retrieval method. Estimates of the statistical error are included in the output files for each data point. These generally vary from 0.2 K to 1 K. Comparisons with dropsonde profiles shows mean differences within this range.
- Mean difference between MTP and dropsonde temperature profiles in PREDICT (475 comparisons -- preliminary)
- Response time: 1 scan every 17 seconds
- Precision:
- Other measurement characteristics (comments on signal/noise, bias limits, etc):

Description of Software, Data Handling, and Data Flow:
Raw data (counts) from three channels
Calibration applied using target brightness temp and ambient measurement from aircraft sensors
Large set of historical radiosondes acquired for region and season; run through radiative transfer model to calculate corresponding brightness temperature profile
Retrieval coefficients generated from modeled brightness temperature profiles (i.e., regression coefficients relate brightness temperature to physical temperature)
Identify best match between measured brightness temperature profile and modeled brightness temperature profile
Apply retrieval coefficients from best match to measured brightness temperature profile to obtain physical temperature profile
Software Components (data acquisition, display, processing, and analysis):
VisualBasic
Real-time Data Acquisition -- straightforward
Display -- profiles, temperature curtain plots, isentropes, housekeeping variables
Processing -- multi-stage with multiple software components (RAOBget, RAOBmanager, RCcalc, MTPbin, MTPsim, some interim calculations in Excel spreadsheets)
Data Processing Chain (from flight to archival):
Pre-project -- acquire raobs in region and season of project. Generate retrieval coefficients for preliminary, real-time retrievals
Field -- Process data post-flight
Post-project --
Select an in situ temperature measurement for use in gain calculation.
Acquire raobs near flight tracks plus large set of "similar" raobs.
Generate final retrieval coefficients.
Initial processing of each flight, generate additional retrieval coefficients as needed.
Determine side lobe errors, apply corrections, reprocess.
Determine errors arising from statistical retrieval process.
Edit suspicious scans manually.
QA Procedures and Needs:
Data quality report released following each project. Example at: http://mtp.mjmahoney.net/www/missions/predict/predict.html

Microwave Temperature Profiler

Instrument Description

Identifying Information

Measurements Made and Methods Used

Lead Contacts

Documentation