We propose to develop an imaging spectrograph to measure the vertical and horizontal distributions of ozone at altitudes of 10 - 50 km during an Arctic winter night. The instrument is deployed by parachute from a sounding rocket at apogee near 80 km. Ozone concentrations are determined from stellar occultation measurements by means of a tomographic technique. The launch site for the mission  will be Churchill, Manitoba.

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-Quantify the spatial and temporal variations of ozone (especially in the low stratosphere region?) and its effects on the global ozone balance as required by existing theoretical models of global ozone trends.

Early models of ozone concentrations are limited in so far as their ability to include the effects of atmospheric pollutants which have markedly increased in the last 10-20 years.  More recent models provide a more satisfactory prediction of ozone concentrations, but questions remain whether the ozone trends truly indicate that the concentrations have changed to a detectable degree.  In 1988, The NASA/WMO Ozone Trends Panel reported their findings of ozone trends in the Northern Hemisphere over the period of 1969 to 1986.  The greatest variations were observed in the latitude band 53-64 N during winter where decreases reached as much as 8.3 per cent [1].  The ozone depletions implied were correlated with measured stratospheric temperature changes. The Panel also inferred long-term changes in ozone profiles although the data available was limited.  In the latitude band of 20-50 in both hemispheres, the satellite data suggested a decrease of about 2.5 +/- 1 percent at about 40 km from 1979/1981 to 1984/1987 [1].  Seasonal trends in northern regions show depletions exceeding 6 percent at high latitudes during the winter months.  

Two natural phenomenon are known which affect ozone concentrations:  the eleven year solar cycle and the directional shift of tropical winds.  Changes of up to 2 percent have been suggested due to variations in solar ultraviolet intensities.  When tropical winds in the lower stratosphere switch from east to west about every 26 months, a typical column abundance variation would be around 2.7 percent for mid-latitudes. In addition, temperature measurements by the Solar Mesospheric Explorer (SME) satellite from January to June 1982, show that global ozone concentrations changes from day to day, and with the seasons, and the principal cause is the variation in atmospheric temperature.  Ozone concentrations are linked with temperature by an inverse relationship, which is observed as change with seasons as well as in orbit-to-orbit variations when significant temperature events occur such as stratospheric warmings.  
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Despite a wealth of experimental data on ozone distribution currently there are no global altitude resolved measurements of ozone. TOMS is producing now outstanding maps of total tropospheric ozone but they are of low accuracy (of the order of 50 %)  and provide little detail on altitude distributions.  Currently existing models of ozone dynamics predict large vertical (in 2-3 km) and horizontal (100-500 km) variations of ozone distributions.  They also predict an importance of low amplitude (of the order of 10 %) variations of ozone concentrations in the low stratosphere.  For further validation and constraint of theoretical and computational models for global ozone trends it is imperative to possess experimental data with horizontal resolution of ~ 100 's km and vertical resolution of 2-3 km with overall precision less than 10 %.  

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?Elucidate the role of "nighttime species" NO2 and NO3 in the global ozone dynamics    

The scientific objective of the NiteOwl mission is to determine ozone column densities and vertical profiles.  However, several trace species have significant absorption cross sections within our spectral region of  400-780 nm which makes the recovery of these distributions a possibility.  Odd-nitrogen species (NO + NO2) show sharp variations at high latitudes in winter that are not reproduced in models that consider only homogenous gas-phase chemistry [1]. Nitrogen dioxide has a broad absorption feature in the 250-600 nm range.  At sunset, NO reacts with ozone to produce NO2.  Measurements of stratospheric NO2 at night have been performed using visible absorption spectroscopy from balloons with a stellar occultation technique [2].  The nitrate radical, NO3, is virtually immeasurable by day due to its high photolysis rate.  Nighttime measurements have been reported by balloon platforms using the star and planet occultation technique at 662 nm [3].  Ozone reacts with NO2 to form NO3 which is of significance in testing atmospheric models to infer the partnership of these constituents in photochemical reactions.  The diurnal variations of these radicals provide information of the coupling between stratospheric Cl-N-H chemistry and long-term transport processes [1, p.146].  High-speed stratospheric transport (SST) has become an issue in the perturbation of stratospheric ozone concentrations, and NO2 measurements at altitudes of 15-20 km are central to the assessment of the impact of SST.  
Nighttime profiles of NO2 and NO3 in the winter polar region would assist the quantification of the NOx source [4].  

Interesting note:  “SAGE III will provide the first global measurements of the vertical profile of NO3.  By viewing the moon in occultation, NO3 profiles from 20 to 55 km will be measured.  Because of its large photolysis rate, NO3 is primarily at nighttime species and is virtually immeasurable during the day.  Consequently, the global distribution of NO3 has never been measured.  The few isolated measurements of NO3 have been controversial since the first observations by Noxon et al (1978).” (Taken directly out of [4]).
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National Space Science and Technology Objectives:

-Maximize training potential  for students and young researchers by providing them wide opportunities for project development in the environment of a multidisciplinary team comprising academic and industrial partners 

-Develop in Canadian industrial sector a potential  to create and manufacture  a  relatively  low-cost microsatellite-based system for high-resolution global ozone monitoring, drawing upon the national capabilities 
 
International Collaboration Objectives:

-Maintain and increase Canadian involvement in the international efforts to understand and predict global ozone trends via providing it with high quality data on spatial ozone distributions

Public Service and Educational Outreach Objectives:

-Increase public awareness of space science missions via communicating issues involved in ozone depletion

This project will further the Canadian contribution to the study of internationally relevant research and is sure to be of benefit to all interested parties, including Canadian technological industries, academia, government agencies and the business community. The benefits are further compounded by both increasing the global exposure of the Canadian Space Agency while maintaining Canadian ownership of the knowledge acquired with most of the money remaining in this country.

It is hoped that this type of instrument and analysis will lead to a relatively  low-cost microsatellite-based system for global ozone monitoring, drawing upon the national capabilities of Canadian universities and industry.

References

.	R.P. Wayne, ed., “Chemistry of the Atmospheres”, Clarendon Press: Oxford, 1991, p.178.
.	J.P. Naudet, P. Rigaud, D. Huguenin, “Stratospheric NO2 at Night From Balloons”, J.Geophys.Res., 89, 2583-2587, 1984.
.	J.P. Naudet, P. Rigaud, M. Pirre, D. Huguenin, “Altitude Distribution of Stratospheric NO3 1. Observations of NO3 and Related Species”, J.Geophys.Res. 94, 6374-6382, 1989.
.	excerpt from a SAGE website (not sure which one, but I could find it if we are referencing websites)