This paper discusses the meaning of filter and covariance consistency and metrics for quantifying covariance consistency. Methodologies for testing and verifying (monitoring) covariance consistency will be explained and contrasted. Possible methodologies with simulated data sets representing hypothetical sensors tracking simulated targets
will be demonstrated. One key methodology relies on statistical hypothesis testing of Mahalanobis distances computed for innovation vectors and state vectors. The focus will be on two important contributors to filter inconsistency: sensor bias and a "scaling factor," which can be an important source of inconsistency in a well-behaved unbiased filter. Using these simulated data sets the problems encountered with
testing the innovation vectors in the presence of sensor biases will be demonstrated, underscoring the need to focus the tests for sensor biases on the state vectors instead. It will also be shown that tests of innovations can be reliable in determining the scaling factor. A way to remove bias effects in consistency tests applied to tracker state vectors will be
demonstrated as well.
The Polar Ozone and Aerosol Measurement [POAM II] instrument has been measuring the
vertical distribution of aerosols, poiar stratospheric clouds [PSC], ozone, as well as several other
atmospheric species since autumn 1993. The approach used to identify PSCs and polar mesospheric
clouds [PMCs] from POAM II measurements will be described along a presentation of some of the
early results of this high altitude cloud measurements. It is believed that the POAM II measurements
of PMCs represent the first reported observations of PMCs directly by extinction; all previous
observations utilized scattering.
The polar ozone and measurement (POAM II) instrument has been collecting data on the vertical distribution of ozone and other species in the polar stratosphere since its launch on the SPOT 3 satellite early in autumn 1993. POAM II makes solar occulation measurements at nine wavelengths from 35 to 1059 nm, allowing it to retrieve ozone, aerosols, water vapor, and nitrogen dioxide with about a 1 km vertical resolution. We will present data on the development and dissipation of the Antarctic ozone hole. We find that the bulk of the depletion occurred during the month of September, with ozone destruction rates exceeding 2% per day. The POAM II measurements clearly demonstrate the strong containment properties of the polar vortex.
The polar ozone and aerosol measurement experiment (POAM II) was launched on the SPOT 3 satellite on 25 September 1993. POAM II is designed to measure the vertical profiles of the polar ozone, aerosols, water vapor, nitrogen dioxide, atmospheric density and temperature in the stratosphere and upper troposphere. It makes solar occultation measurements in nine channels defined by narrow-band filters. The field of view is 0.01 by 1.2 degrees, with an instantaneous vertical resolution of 0.6 km at the tangent point in the earth's atmosphere. The SPOT 3 satellite is in a 98.7-degree inclined sun-synchronous orbit at an altitude of 833 km. From the measured transmissions, it is possible to determine the density profiles of aerosols, O3, H2O, and NO2. Using the assumption of uniformly mixed oxygen, we are also able to determine the temperature. We present details of the POAM II instrument design, including the optical configuration, electronics and measurement accuracy. We also present preliminary results from the occultation measurements made to date.