MANTRA - Mission Overview

MANTRA (Middle Atmosphere Nitrogen TRend Assessment) is a balloon mission to investigate changes in the concentrations of ozone and other compounds in the stratosphere. It will involve the launch of a large unmanned balloon from Vanscoy, Saskatchewan in late August 1998. The balloon will carry a payload of instruments to measure atmospheric composition, and will float at an altitude of 35-40 km for one day.

Stratospheric ozone depletion has received considerable attention since the 1985 discovery of catastrophic reductions in ozone concentration over Antarctica during spring (the "Antarctic ozone hole"). MANTRA will focus on mid-latitude stratospheric ozone, which has declined by about 10% over the past 20 years. Losses of ozone at mid-latitudes have been much greater than can be accounted for by current theories regarding ozone destruction. This is important because current predictions for the future evolution of the ozone layer are based on these theories, and form the scientific basis for the terms of the Montreal Protocol, which regulates the global production and release of ozone-depleting substances.

With MANTRA, we plan to investigate possible causes for the lack of agreement between theory and observations by flying six instruments, three of which were flown on balloons in the 1970s and early 1980s (NO₂ spectrophotometer, HNO₃ radiometer, OH spectrometer), and three of which employ newer technology (photodiode array spectrometer, acousto-optic tunable filter spectrometer, Fourier transform interferometer). This will allow a dual intercomparison: one between measurements obtained by the same instruments after an interval of 15-20 years, and the other between the old and new measurement techniques. We plan to launch the balloon before sunrise so that it reaches float altitude (about 39 km for a balloon volume of 11.6 million cubic feet) in time for several of the instruments to track the sun as it rises. The balloon will then remain at this altitude for the day, allowing several instruments to scan the Earth's horizon through a range of altitudes, recording spectra of scattered sunlight. After again tracking the sun as it sets, the balloon payload will begin a parachute descent so that all of the instruments should be recovered at the end of the mission.

The primary gases of interest are ozone, NO₂, HNO₃, ClONO₂, and HCl, but a number of other important gases will also be measured by the balloon-borne instruments. Detailed background atmospheric studies will also be conducted using ozonesondes, radiosondes, and aerosol sondes, as well as a ground-based Brewer spectrophotometer and a zenith-sky spectrometer. All of the data will then be used in an extensive modelling effort that will take place after the experimental work has been completed. This will focus on ddetermining whether there have been long-term changes in the concentrations of those nitrogen compounds that indirectly control ozone destruction. If observed, such changes could help explain the unexpectedly large values of mid-latitude ozone depletion observed during the last two decades.

MANTRA has been funded under the Small Payloads Program of the Canadian Space Agency (CSA), and has received additional support from the Atmospheric Environment Service (AES) of Environment Canada, and the Centre for Research in Earth and Space Technology (CRESTech).

The Principal Investigator is Kimberly Strong (University of Toronto), but the project is a collaborative effort involving Co-Investigators Jim Drummond (University of Toronto), Jack McConnell (York University), Tom McElroy (AES), Brian Solheim (CRESTech/York University), and Frank Murcray (University of Denver), with Scientific Instrumentation Limited of Saskatoon as the Industrial Partner.

Maintained by: Kimberly Strong
Last updated: 23 July 1998