MicroMAPS Test Flight

Results of a Test Flight of a MicroMAPS Breadboard

NASA Ames DC 8 at Moffat Field

Installation of the MicroMAPS Breadboard in the cargo hold of the DC 8

In October 1994 a breadboard model of MicroMAPS was flown on the NASA Ames DC-8 research aircraft in a underflight of the MAPS which flew on STS68. Approximately 40,000 line km of CO and N2O measurements were made over a 10 day period over the US and southern Canada.

Data was both observed in real time and recorded digitally on the notebook computer data terminal hard disk during most of the MicroMAPS breadboard flight. The shell program that recorded the data also partially reduced the data so that cell ratio's could be observed. These ratios were recorded in a flight journal as a backup to the digitally recorded data. This "real time" feature made it was possible to evaluate the performance of the instrument in flight.

View of the cockpit of the DC 8 & out the window over Montana

View over Pike's Peak in Colorado & Flight trajectory view out front of DC8 during turning manoeuvre

DC 8 Data Acquisition display and MicroMAPS data over Denver

The gas cell/clear cell ratios were observed to increase on ascent and decrease during descent as the thickness of atmosphere between the aircraft and ground increased or decreased. The instrument gave stable ratios at 35,000 feet as the temperature cooled during flight. In fact, even though the instrument was changing in temperature from +30 to as low as -5 during an extended flight no observable effect on calibration was detected. This leads us to conclude that the breadboard functioned through a temperature range of -5 to +30 C which is wider than the predicted on-orbit range.

The flight observations of the changes in CO and N2O to clear cell ratios during ascent and descent validated the operation of the sensor and simulated the on-orbit detection of CO and N2O. In general, in-flight observations confirmed that the instrument was fully functional for 40,000 line km.

MicroMAPS Data For Southern Ontario Oct 8,1994

                                       N2O channel             CO channel

Signal ratio gas/clear Ref BB             0.82                   0.685
Signal ratio gas/clear Atmospheric        1.00                   0.815
Noise in ratio                            0.012                  0.012
DeltaS/S                                  0.22                   0.187
Average at absn coef. used in model       2.1 atm/cm             2.5 atm/cm 
Modulation Efficiency (estimated)         0.6                    0.85
Column amount (atm-cm)                    0.174                  0.088
Column thickness                          9.6 km                 9.6 km
Average column density                    0.65 std atm           0.65 std atm
Mixing Ratio from zero order model        280 ppb average        140 ppb average
Noise equivalent amount  (NEA)            18 ppb                 9 ppb