Overview of the MOPITT-A instrument
MOPITT-A (Measurements of Pollutants In The Troposphere -Airborne simulator) is a remote sounding instrument which measures total tropospheric column amount of CH4 and CO, as well as upper and middle tropospheric levels of CO, from the forward segment of an ER-2 aircraft wing-pod.
The instrument is a four channel version of the MOPITT space instrument scheduled for flight on the Terra platform in July 1999 (Drummond, 1996). The airborne instrument is designed to validate MOPITT satellite data and perform independent studies on a smaller scale.
(1) Channels. MOPITT-A is a correlation radiometer (CR) with 4 channels in the infrared and near-infrared (Table 1). It performs:
(2) Correlation cells. MOPITT-A uses three correlation cells: one pressure-modulated cell (PMC) and two length-modulated cells (LMC). The PMC has an extensive and successful history on many satellite remote sounding instruments (Drummond, 1996). The LMC has been designed and extensively characterised at the University of Toronto, both with the MOPITT and MOPITT-A instruments and with a ground based instrument (Tolton, 1999).
(3) Field-of-view. All channels have linear array of 4 pixels, with an angular field-of-view of 1.8°´1.8°, yielding a ground footprint of 630´2520m.
(4) Accuracy. Expected accuracy is 10% for CO and 1% for CH4.
MOPITT-A channel characteristics:
Channel |
1 |
2 |
3 |
4 |
Gas |
CO |
CO |
CO |
CH4 |
Measurement |
Middle troposphere (thermal radiation) |
Column (reflected solar radiation) |
Upper troposphere (thermal radiation) |
Column (reflected solar radiation) |
Correlation cell pressure (kPa) |
80 |
80 |
3.8 |
80 |
Mid-wavenumber (cm-1) |
2166 |
4285 |
2166 |
4430 |
Mid-wavelength (mm) |
4.617 |
2.334 |
4.617 |
2.258 |
Modulator |
LMC 1 |
LMC 1 |
PMC |
LMC 2 |
Last updated Aug 5th 1999 by Loic Jounot.