NIGHTSKY IMAGING TOMOGRAPHY EXPERIMENT

TO MEASURE OZONE WITH STARLIGHT

NiteOwl

A proposal for the Small Payloads Program

of the Canadian Space Agency

Submitted by:

D.P. Steele

Department of Physics and Engineering Physics

University of Saskatchewan

116 Science Place

Saskatoon, SK S7N 5E2

for the NiteOwl Submission Team

January 10, 1997

_______________________________

R.P. MacKinnon, Vice-President (Academic)

University of Saskatchewan

________________________________

F. Berruti, Dean of Engineering

University of Saskatchewan

________________________________

B.R. Neal, Associate Dean of Arts and Sciences (Academic)

University of Saskatchewan

________________________________

M.J. Owen, Director of Research Services

University of Saskatchewan

________________________________

W. Irwin, Vice-President (Marketing and Sales)

SCI-TEC Instruments, Inc.

NiteOwl Submission Team

H.S. Caplan, M. Huber, A.V. Koustov, E.B. McDougall, J.J. Offiong, A.I. Smolyakov,

M.M. White

Department of Physics and Engineering Physics, University of Saskatchewan

116 Science Place, Saskatoon, SK S7N 5E2

R.J. Bolton, J.E. Giesbrecht, H.C. Wood

Department of Electrical Engineering, University of Saskatchewan

57 Campus Drive, Saskatoon, SK S7N 5A9

J.D. Bugg, A.T. Dolovich, J.A. Steele

Department of Mechanical Engineering, University of Saskatchewan

57 Campus Drive, Saskatoon, SK S7N 5A9

C.E. Soteros, R. Srinivasan

Department of Mathematics and Statistics, University of Saskatchewan

106 Wiggins Road, Saskatoon, SK S7N 5E6

J.K. Chan, D.P. Harris, and M.J. Painter

College of Commerce, University of Saskatchewan

25 Campus Drive, Saskatoon, SK S7N 5A7

E.V. Ivanov, J.E. Johnston, D.J. Sniezek

SCI-TEC Instruments Inc.

1526 Fletcher Road, Saskatoon, SK S7M 5M1

In the last two decades, ozone chemistry has become a public concern, as major ozone depletion has taken place both in the polar regions and elsewhere. The associated potential for human health problems and disruption of plant life, including effects on the agriculture, forestry, and fisheries industries, have made this subject one of intense public interest. In light of the potentially disastrous consequences of ozone depletion, both for key sectors of the national economy and for public health, it is imperative to provide an effective, low cost means of global ozone monitoring which can provide data on ozone levels both to the Canadian public and to the scientific community. It is worth noting that recent specialized ozone satellite missions are not able to meet this requirement fully because of their extreme complexity and high scientific specialization. Due to the extremely high costs associated with these missions they are normally conducted with broad international cooperation.

Major advances in the study of atmospheric ozone have been made since its inception in the 1920s, progressing from ground based observations to balloon, aircraft, rocket, and satellite platforms. Observations from the ground are convenient and provide long term data but cover only small geographic areas and cannot provide a global picture of the ozone distribution and its complex dynamical variations. Satellite instruments are capable of remotely sensing both total ozone levels and height distributions, providing comprehensive current data over most of the Earth. Over the last three decades many satellite missions have measured ozone[1], and several other missions are now operating or in preparation [2]. Significant progress has been achieved in understanding the major processes involved in ozone dynamics. Despite this, no comprehensive model capable of predicting long term trends of the ozone layer exists. Recent satellite missions are directed toward obtaining comprehensive data which will support the development of such models.

1.2 Mission Objectives

The goal of the proposed project is to develop and validate an instrument capable of providing data on spatial and temporal variations of ozone during an Arctic winter. The instrument will be deployed on a parachute from a sounding rocket. The ultimate goal is to create within the Canadian space science community and Canadian industry a capability for construction and deployment of a microsatellite-based system for global ozone monitoring. Such a system would be an efficient low-cost national alternative to the present systems (TOMS, GOME), and those in the planning stages (GOMOS, SCIAMACHY) and would provide important and timely information about the ozone layer to both the Canadian public and the atmospheric science community.

We propose to develop an imaging spectrograph to measure the vertical and horizontal distribution of ozone at altitudes from 10 to 50 km during an Arctic winter night. The instrument will be deployed on a parachute from a sounding rocket at apogee near 80 km. Ozone concentrations are determined from stellar occultation measurements by a tomographic technique. The mission will be carried out from SpacePort Canada at Churchill, Manitoba.

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

Despite of wealth of experimental data on ozone distribution currently there are no global altidute resolved measurements of ozone. TOMS is now producing 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 horisontal (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 contraint of theoretical and computational models for global ozone trends it is imperative to possess experimental data with horizontal resolution of the order of 100 km and vertical resolution of 2-3 km with overall precision better than 10 %.

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

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

International Collaboration Objectives:

-Maintain and increase Canadian involment 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.

1.3 Global Ozone/Dynamics/Scientific Issues

There are two main regions where ozone is prevalent in the atmosphere: stratospheric ozone lying in the region between altitudes of 10 - 50 km and tropospheric ozone below 10 km. One commonly refers to the stratospheric portion as the "ozone layer". This layer is responsible for the absorption of biologically damaging ultraviolet sunlight, known as UV-B. The result of the ozone absorption is a heating in this region of the atmosphere which is ultimately responsible for the temperature structure of the stratosphere.

Total column ozone abundances have been analyzed from 1979 to present showing a general downward trend. From both ground-based and satellite measurements, a 4-5% decrease per decade has been observed for both hemispheres at mid-latitudes [1]. Furthermore, there are annual variations in ozone concentrations with most destruction of ozone occurring during the winter/spring seasons in both hemispheres. This coincides with the formation of extremely cold, stable vortices. Under these conditions, polar stratospheric clouds (PSCs) are able to form. PSCs allow chemistry to occur on surfaces (ice, nitrate and sulfate particles) as well as in the gas phase. Examples include the conversion of inert chlorine to its reactive forms and the holding cycles of nitrogen dioxide which make this species unavailable to stop the destruction of ozone. This is the main cause of Antarctic ozone depletion, due to the extreme cold of this region and thus high occurrences of PSCs. In the Arctic, the temperatures are higher and the possibility of PSC formation is less. However, chlorine and other reactive species have similar concentrations in both hemispheres. Should the Arctic stratospheric temperatures drop to those characteristic of the Antarctic, we could expect the same destruction of the ozone layer. Due to the significance of these formations in the Arctic, it is our intention to map any of these formations that we might encounter.

Ozone suffers diurnal variations as well. (These are the concerns with validation with Brewer technology: what will happen to concentrations if we compare daytime Brewer to our data? Will we have to go with moonlit Brewer?) Several species undergo large diurnal variations. Measurements of radicals and other representatives from the important chemical family, NOx, will provide valuable information to enhance the interpretation of the ozone results.

The conversion of NO to NO2 at night is a rapid process, while the photolysis rate of NO3 is large, such that NO3 is nearly unmeasurable during the day. The object of our stellar occultation method is to determine vertical profiles of these nighttime species. Both NO2 and NO3 have strong absorption features within the spectral range of 400-700 nm.At a tangent altitude of 24 km, NO2 absorbs an estimated 7% at 431 nm (without scattering). This should be detectable with the target sensitivity of our instrument. The full spectral range (400-780 nm) of our instrument allows better separation amongst atmospheric constituents, including aerosols, and does not rely on unique spectral signatures.

Extinction effects in the atmosphere (including Rayleigh and Mie scattering) will be included in our retrieval algorithms. Rayleigh scattering involves molecules which are much smaller than the incident wavelength. The scattering cross-section is well known, and we have confidence in our models of this effect. Mie scattering involves aerosol particles which are comparable or larger than the incident wavelength. The size, shape and density of the scattering particles all affect the scattering cross-section. A simple Mie scattering model will be included in our analysis. The advantage that our mission provides in order to map PSCs or determine the best Mie scattering model is that there will be more than one viewing angle for each irradiance measurement. The viewing angle dependence of the retrieved aerosol optical thickness has been suggested as evidence of particle nonsphericity and may also be used to reject unreasonable aerosol models (GRL,22,1077,1995 - practically word for word). The substantial effect of PSCs on the abundance of trace gases in the stratosphere (GRL,20,2059,1993) may also be revealed by our measurements should a PSC occur.

2 The NiteOwl Experiment

The NiteOwl experiment is to be launched from SpacePort Canada (Churchill, MB) aboard an Orion rocket. This rocket will take the payload to an altitude of 80km. From apogee the payload will descend using a parachute specially designed to provide a low spin rate. Measurements of stellar spectra attenuated by atmospheric absorption will be taken using an imaging spectrograph (ISG) viewing horizontally. As the payload rotates the ISG will scan the full horizon. The position of the payload will be monitored using an onboard Global Positioning System (GPS) receiver, which will also facilitate post-flight recovery. An attitude video camera (AVC) in the payload will image the star field to determine the look direction of the ISG. Data transmitted to the ground will include measurements made by the ISG and the GPS receiver, an attitude video camera (AVC), pressure and temperature sensors, and possibly a chemiluminescent ozonesonde to measure ozone in situ. A block diagram of the entire instrument is shown in Figure 1-2.

The ISG will disperse incident starlight using a transmission diffraction grating and focus the light onto a Charge Coupled Device (CCD) detector which will measure the spectral irradiance after absorption by the atmosphere. The spectral resolution of the measurements will be 3.4 nm, and the wavelength range from 400 to 780 nm will span the Chappuis bands of ozone as well as absorption bands of NO2 at the shortest wavelengths and of NO3 at the longer wavelengths. The CCD detector readout will undergo lossless compression and will be transmitted, together with the data from the GPS receiver and the other sensors, via a telemetry unit interface to the telemetry system, which will transmit the data to a receiving system on the ground over an S-band PCM-FM link.

2.1 Description of Experimental Methods

The NiteOwl experiment will measure ozone concentrations using a stellar occultation technique. The rotation of the payload during its descent through the atmosphere allows observations of stars all around the horizon, and measurements of ozone column concentrations at all azimuths where sufficiently bright stars are seen. Measurements may be made at any local time during the night, because the method does not depend on tracking any particular star, or on the position of the sun or moon. In each 1-s image from the ISG several stars will be visible; however, the signal-to-noise ratio (SNR) required to do accurate inversion will only be achieved for stars of magnitude 3.0 or brighter. Each star provides a set of lines of sight through the atmosphere. The combination of all the lines of sight through the region to be reconstructed provides the raw data on which tomographic analysis will be performed.

The initial measurement of each stellar spectrum from above the stratospheric ozone layer provides a reference spectrum for all subsequent observations of that star.Subsequent measurements of a star's spectrum from within the stratospheric ozone layer are divided by the initial (unabsorbed) spectrum to yield fractional transmissions, from which column concentrations of O3 (and possibly NO2, NO3, and M) may be derived. In this way the ISG is self-calibrating, as there is no dependence on absolute sensitivity of the instrument.

The occultation technique to be used for the NiteOwl mission is based on taking the ratio of the spectral irradiance I( ) from a particular star when seen through the atmosphere, to the unattenuated spectral irradiance from the same star when seen above the atmosphere I0( ) (Eq. 1-1). where ( ) is the absorption cross section per molecule and N is the column number density of the absorbing species (cm-2). If the atmospheric attenuation is due solely to ozone, the column density of ozone in the path may be calculated from Eq. 1-1. If other species absorb significant amounts of radiation at the wavelength of interest then additional terms must be added (Eq. 1-2):

As starlight passes through an absorbing atmosphere, the irradiance decays exponentially with the amounts of ozone and other absorbing/scattering species along the light path determining the degree of attenuation. Working with the logarithm of the ratio of spectral irradiances transforms the governing equation to a linear one, permitting a tomographic solution process.

The tomographic reconstruction of the ozone distribution presents a number of challenges. These arise from the slenderness and curvature of the domain, the dominance of the vertical component of the ozone density gradients, the very weak absorption cross section in the Chappuis bands necessitating large column lengths, and the requirement to reconstruct geographic variations using a small range of source elevation angles. These factors conspire to make the problem ill- posed.

Because each potential source star must be viewed at least once above the stratosphere, the 80 km apogee limits data gathering to stars which are no lower than 5 below the horizon. (Note: horizon = the set of all points 90 from the local zenith.) Assuming such a star is present and bright enough and observed by the instrument, the lowest of its rays that clear the aerosol contaminated region below 10 km altitude will provide data on ozone no further away than 1200 km from the instrument and then only at 40 km altitude. Above the horizon, elevation angles greater than 6 pass through too little atmosphere for attenuation to be clearly different from noise.

If ozone varied only with altitude, the tomographical problem would be governed by Abel's integral equation [Vest 1979] which is only moderately ill-posed. Our simulations, however, show that if geographic ozone variation is at all significant, a purely vertical inversion yields poor results. To incorporate the geographical variation in ozone, a technique other than Abel inversion must be used.

2.2 Instruments

The ISG will image starlight from a field of view subtending 15 horizontally and about 12 vertically. Collimated light from each star in the field of view is dispersed by a low-resolution transmission grating, and then focused onto the CCD detector by a fast, large-aperture objective lens. The pitch of the grating and the focal length of the objective lens will be chosen to provide a spectral resolution of 3-5 nm per CCD pixel.

A GPS receiver, to be provided by Bristol Aerospace Ltd. (BAL), will allow real-time determination of the experiment position and velocity in three dimensions with 100-m accuracy.

A Xybion intensified video camera identical to that flown on the OEDIPUS-C mission will be provided by BAL as an AVC to determine the pointing direction of the ISG. The knowledge base required for attitude determination from the video signal was developed for the GEMINI mission and resides at the University of Saskatchewan.

Subject to availability and payload mass and power restrictions, we intend to fly a chemiluminescent ozonesonde [Hilsenrath and Kirschner 1980], to provide in situ validation of our optically determined ozone profiles. This instrument is the only technique available for routine nighttime in situ ozone measurements above balloon altitudes.

In order to determine other trace species concentrations, it is required that temperature or pressure be measured. Although the inversion technique could also provide some measure of these parameters, several species are extremely sensitive to photolysis rate dependent on the temperature. With this requirement on the precision of the temperature survey, it is best to provide a definite means of measurement. A standard thermistor, such as that used in the Super Loki datasonde, will allow the measurement of temperature in a simple, effective and reliable way that would not place significant burden on the cost or payload weight of the mission.

2.3 Expected Performance

2.3.1 NiteOwl Instruments

Falling from an apogee of 80 km, the NiteOwl instrument will scan the horizon, building a database of reference stellar spectra as it falls through the mesosphere. The instrument will image unocculted stars of magnitude 3.0 or brighter with a minimum SNR of 100:1 while rotating at a rate of 6 per second or less. The spectral resolution will be 5 nm or better, and the angular resolution in elevation will be 1 arcmin.

The chemiluminescent ozonesonde provides ozone profiles over the altitude range from 65 to 20 km, with about 12% accuracy and 6% precision.

2.3.2 Tomographic Reconstruction

The distribution of stars around the horizon depends on the latitude of the launch site and the local sidereal time (LST) during the flight. For a launch from SpacePort Canada (Churchill, MB) during a dark-moon period in the winter of 1998-99, LST windows exist for which the horizon distributions of stars brighter than 3rd magnitude contain no gaps wider than 40 of azimuth (12% of the horizon, and sectors of azimuth where suitable stars occur at azimuth spacings of 5 - 10 .

To provide estimates of the reconstruction error, we developed a preliminary code to generate synthetic noisy tomographic data using the vertical ozone density profile from the GOMOS model [Kyrölä 1993] with a gentle geographic variation superimposed. We then attempted to reconstruct the ozone density distribution within the domain from the noisy data.

A classical tomographical approach was used, i.e., we tracked starlight paths through the domain generating line integrals, discretized the field spatially (thus reducing the governing integral transform to a system of linear equations), and added random noise to the data corresponding to an RMS SNR of 100:1 before applying solution techniques. Simplifying assumptions included no earth rotation during the experiment and no lateral payload drift, though this will clearly not be the case in practice.

The domain reconstructed lies between 10 and 40 km altitude and between a hypothetical vertical line of instrument trajectory and another locally vertical line 1200 km away. These boundaries define an annular sector. The domain is defined by sweeping this sector between two planes, each of constant azimuth, about the instrument trajectory line. These planes are close enough together that ozone does not vary significantly between them, but far enough apart to include two stars near the horizon at +1 and -3 elevation angles. From an analysis of the star horizons available at Churchill and current estimates of geographic ozone variations, 5 is a reasonable width.

(A picture here would be good. We will supply one.)

Two approaches to solving the linear systems yielded very encouraging results; both used regularization [Craig and Brown 1986; Dubovikova and Dubovikov 1987 ] to stabilize the systems. One approach modelled the gentle geographic distribution using an assumed form with one degree of freedom. The second approach used a full domain discretization.

Our simulations give us confidence that for a S/N ratio of 100:1, the average vertical ozone density profile may be determined to within 15% of true values with a resolution of 3 km.

The ultimate accuracy in reconstructing the geographic distribution will depend on many factors including the nature of the actual geographic distribution (for which little is known a priori), the type of regularization used, and the model upon which inversion is based. Alternatives to regularization, such as the maximum probability method [McDade and Llewellyn 1993], are available as well. The determination of the optimum model and form of inversion, taking expected payload drift and star rising and setting into account, will be made during Phase A.

2.4 Data Acquisition and Processing

Data will be telemetered from the payload on two frequencies. Losslessly compressed data from the imaging spectrograph (ISG) will be merged with GPS data, and possibly with data from the chemiluminescent ozonesonde, and transmitted to the ground using bi-phase PCM-FM telemetry at an S-band frequency. In addition, the 2-MHz bandwidth analog video signal from the AVC may be RF-multiplexed onto the same antenna, or transmitted to the ground on an S-band carrier from another antenna. The raw telemetry data will be recorded on tape as well as being decommutated in real time.

The time-stamped AVC data will determine the look direction of the ISG at each moment. This technique was used successfully in the GEMINI project. The combination of the GPS- determined position-velocity data and the AVC attitudes defines precisely the atmospheric column along which the total ozone concentration is measured, as well as the rate of change of the column.

The ISG images must be decompressed and spectrally inverted to determine the optically absorbing species and their corresponding column densities. The first step is to remove the blurring caused by payload spin during the 1-s exposure time. This blurring will be primarily horizontal, and therefore perpendicular to the vertical wavelength dispersion caused by the horizontal orientation of the grating rulings. Therefore, adjacent spectra can be shifted and summed to compensate for the motion of the ISG. This is accomplished by referring to the angular deflections obtained over time from the AVC results. This summation will simultaneously intensify the measured spectra and tend to cancel the readout noise present on each measured spectrum.

3 NiteOwl in the Canadian and International Context

Ozone monitoring in Canada is currently carried out using a network of ground-based Brewer ozone spectrophotometers, part of the worldwide Brewer network which is coordinated by Environment Canada scientists at Atmospheric Environment Service. Brewers routinely use both the sun and moon as sources, and a stellar Brewer is nearing completion. Various balloon- and rocket- borne ozone sondes for daytime use have also been developed in Canada in the past.

Planned space missions such as ODIN and MOPITT also address the need to measure ozone and other key trace gases in the upper troposphere and lower stratosphere region. (Words will be added here when I have time to learn more about MOPITT.)

The Total Ozone Mapping Spectrometer (TOMS) on Nimbus 7 provided nearly fifteen years of accurate global ozone maps using backscattered ultraviolet (BUV) observations. Successor instruments on the NASA Earth Probe and Japanese Advanced Earth Observing Satellite (ADEOS) continue to monitor total column ozone.

The Halogen Occultation Experiment (HALOE) on the Upper Atmosphere Research Satellite (UARS) measures altitude profiles of several minor species, including O3 and NO2, from the ground through the stratopause using a solar occultation technique. HALOE observations are restricted to the terminator, and the inclination of the UARS orbit limits latitude coverage 60 S to 60 N.

GOME?

SCIAMACHY?

The GOMOS instrument on the European Space Agency ENVISAT platform will measure ozone and numerous other minor constituents using the stellar occultation technique, as does NiteOwl. The large number of target species necessitates much higher spectral resolution and coverage. Words about the cost?

In an attempt to reduce costs while still realizing similar GOMOS science objectives, the COALA study is intended to make complementary nighttime or validation measurements for other missions. Although the NiteOwl objectives also include nighttime ozone retrieval, we plan to provide similar science results at a reduced cost from a Canadian perspective.

It is our intention to provide a Canadian polar night ozone measurement by tomographic technique. A key element for quality tomographic results is redundant measurements. These would be of the same atmospheric cell taken from different vantage points during descent and improved by multiple lines-of-sight provided by the various stars in our field of view. Presently, this is accomplished by making observations over multiple passes of the same area. The NiteOwl payload will rotate as it descends, thereby getting multiple looks through the same cells, each from a different angle. In addition, the broad ozone absorption feature of the Chappuis band (450 - 750 nm) can be measured satisfactorily with only moderate spectral resolution. This may affect the number of recoverable species but will reduce the cost of the mission.

4 Required Theoretical and Modelling Support

During the Phase A study, at least three modeling exercises will provide important data to the mission. These will deal with simulations of: the kinematics of the payload during descent, the spectral inversion problem and the tomographic inversion problem. Support for these studies will come from existing research funding from sources such as NSERC.

*** questions here: If theoretical and modeling means not funded by CSA SPP program, does that mean the kinematic and detailed tomographic simulation should go in another section? They are pretty central to the whole endeavor and I think they should be funded.****

*This project requires high altitude deployment of a controlled-spin parachute. The local dynamics of the payload (attitude fluctuations) under the influence of atmospheric turbulence has not been modeled to date. There exist statistical models for various upper atmospheric conditions, and the modelling required for NiteOwl will incorporate these to simulate the local payload dynamics during descent.

So far absorption data has been generated using expected constituents of the atmosphere and current data on the corresponding absorption bands. Remaining to be done is the addition of noise to these data, with subsequent inversion to analyze the sensitivity of the process to random and systematic noise.

There are variety of tomographic algorithms available for reconstruction of the ozone distribution from the column density data. A comparison of these as well as a search for alternative techniques to bridge the gaps in the horizontal star distribution would permit the choice of optimal tomographic inversion techniques for our particular mission.

*Tomographic simulation has already been done for small sectors of the horizon having more than one star in them. These have been useful for setting the current expected resolutions for tomographic reconstruction. However, a more detailed simulation needs to be done. This simulation would use the actual star distribution during actual launch windows and include the change in the star positions during the hour or so flight time. In addition, the expected local payload dynamics from the first modelling study could be included. This would provide a much stronger point of reference in establishing appropriateness of the top level science requirements.

5 Required Support Measurements

It is desirable to obtain independent measurements of both total column ozone and ozone profiles for comparison with the results from the NiteOwl experiment. SCI-TEC Instruments Inc. will provide a Mk III Brewer ozone spectrophotometer to measure total column ozone, using solar observations on the days before and after the NiteOwl launch, night-time lunar observations before or after launch, or a combination of solar and lunar observations. In order to use the Mark III Brewer during the same night as the mission, the moon must be 10 above the horizon for at least one hour. Satellite-borne total column ozone measurements from GOME or TOMS would also provide useful support, if the launch occurs late enough in the winter that the SBUV technique can be used at the latitude of Churchill (cf. Fig. 1-1). Weather permitting, the Mk III Brewer ozone spectrophotometer will be used to measure the ozone profile in Umkehr mode.

Meteorological data are also required for launch support and to aid in both the spectral and tomographic inversions. Akjuit Aerospace Inc. will provide regular data on both surface weather and stratospheric winds, the latter at 12-hour intervals. Altitude profiles of temperature and pressure to the stratospause would be useful, and may be obtained from a combination of balloon sounding and satellite-borne sensors. Regional cloud/aerosol data from weather and other operational satellites will also be required to confirm the scattering cross-section in the upper troposphere.

6 Data Analysis and Publication Plan

Before the NiteOwl launch, a number of preliminary studies must be carried out. These will evaluate and optimize the choice of techniques to be used in interpreting synthetic data before the launch, and real data obtained from the mission itself. The results will be publishable.

During the pre-launch phase of NiteOwl, synthetic occultation data will be generated. These data include an assumed distribution of absorbing atmospheric constituents, known atmospheric phenomena as well as expected levels of systematic and random noise. The spectral inversion of these data sets using a variety of techniques will enable evaluation of their abilities to discriminate between absorption features and phenomena not indicative of atmospheric column densities.

Once column densities have been obtained, tomographic reconstruction can be carried out. This will begin with vertical inversion and culminate in an evaluation of an array of tomographic methods for their capability to reproduce the known distributions in the originating synthetic data. These results will be publishable.

The optical configuration to be used with this project is not a common one. Innovative optical design used in this project may form an important part of the larger paper to be prepared on the NiteOwl project. This paper, to be submitted after launch, will include an overview of our mission, design, execution and the data gathered along with some preliminary results of data interpretation. The lessons learned will support the successful design and launch of a Canadian ozone monitoring satellite.

Subsequent to the general mission paper, detailed column density and tomography results will be published along with comparisons to contemporary results obtained by others monitoring the problem of polar stratospheric ozone depletion.

In addition to these results, the data gained from the GPS receiver and the AVC will enable the analysis and publication of the payload dynamics accompanying a high-altitude deployment of a low-spin parachute. This will be a useful advance on the current state of the art.

7 Science Team

7.1 Members of the Science Team

Dr. D.P. Steele (Senior Research Scientist and Adjunct Professor of Physics and Engineering Physics, University of Saskatchewan) is the Principal Investigator of the NiteOwl Team. His areas of specialization and expertise are upper atmospheric physics and optical imaging of atmospheric emissions to derive atmospheric state parameters.

Dr. H.S. Caplan (Professor and Head of Physics and Engineering Physics, University of Saskatchewan) has extensive experience in science administration and project management.

Dr. A.V. Koustov (Assistant Professor of Physics and Engineering Physics, University of Saskatchewan) has expertise in geophysical application of ground-based and satellite measurements to study the structure of the Earth's atmosphere and ionosphere.

Dr. A.I. Smolyakov (Assistant Professor of Physics and Engineering Physics, University of Saskatchewan) has extensive theoretical expertise in the analysis of random processes in plasma environments including neutral turbulence and dynamics of non-linear processes in fluid-like media.

Dr. R.J. Bolton (Professor of Electrical Engineering and Associate Member in Computer Science, University of Saskatchewan) has expertise in VLSI circuit design, pattern recognition techniques, digital circuit design, computer systems and electrical systems integration. He also has experience in the analysis of attitude video camera and on-board CCD data.

Dr. H.C. Wood (Professor and Head of Electrical Engineering and Associate Member in Agricultural and Bioresource Engineering, University of Saskatchewan) has extensive expertise in the development of instrumentation for optical atmospheric studies.

Dr. J.D. Bugg (Associate Professor of Mechanical Engineering, University of Saskatchewan) has expertise in numerical modelling and experimental investigations of thermal/fluid systems.

Dr. A.T. Dolovich (Associate Professor of Mechanical Engineering, University of Saskatchewan) has expertise in the development of tomographic methods for optical measurement and non-destructive testing.

Dr. C.E. Soteros (Associate Professor of Mathematics and Statistics, University of Saskatchewan) has expertise in computer simulation.

Dr. R. Srinivasan (Associate Professor of Mathematics and Statistics, University of Saskatchewan; consultant with AT&T Bell Labs) has extensive expertise in noise modeling, data compression techniques, and inversion algorithms.

Mr. E.V. Ivanov (Senior Research Engineer, SCI-TEC Instruments Inc., Saskatoon) has expertise in optical system design and construction, and balloon-borne optical measurements of stratospheric ozone.

Dr. J.E. Johnston (Senior Research Scientist, SCI-TEC Instruments Inc., Saskatoon) has expertise in both ground-based and space-borne spectroscopy and interferometry applied to chemical composition measurements of the troposphere, stratosphere, and mesosphere.

Mr. D.J. Sniezek (Vice President of Research, Development, and Engineering, SCI-TEC Instruments Inc., Saskatoon) has extensive experience in project management and the development and engineering of optical equipment for atmospheric ozone monitoring.

Dr. M.J. Painter (Assistant Professor of Accounting, College of Commerce) has experience in project management and the supervision of graduate management students.

7.2 Responsibility and Level of Effort

Table 2-1 details the members of the NiteOwl Science Team and their respective areas of responsibility and levels of effort. It should be noted that the proposed Science Team, consisting of faculty members of five departments and three colleges of the University of Saskatchewan as well as senior science and engineering personnel of SCI-TEC Instruments, Inc, bring to the project a very wide range of professional experience and complementary expertise

worked closely

7.3 Graduate Members of the Submission Team

Words about educational aspect of submission preparation: prepared by eight graduate students in four departments and three Colleges at University of Saskatchewan as course work for two special- topics graduate courses.

Table 2-1. The NiteOwl Science Team

Team Member	Responsibility	Level of Effort
D.P. Steele	Project co-ordination, mission planning and science	160 hr/month
H.S. Caplan	Project management	5 hr/month
A.V. Koustov	Instrument calibration and data storage	20 hr/month
A.I. Smolyakov	Mission simulation	20 hr/month
R.J. Bolton	Electrical/electronics design, risk analysis	25 hr/month
H.C. Wood	Design consultation	5 hr/month
J.D. Bugg	Mechanical and thermal design	15 hr/month
A.T. Dolovich	Development of tomographic analysis technique	15 hr/month
C.E. Soteros	Inverse problem	15 hr/month
R. Srinivasan	Data compression, image reconstruction	15 hr/month
E.V. Ivanov	Optical instrument fabrication and testing	15 hr/month
J.E. Johnston	Optical instrument specification and design	30 hr/month
D.J. Sniezek	Management of instrument development	5 hr/month
M.J. Painter	Supervision of graduate financial management students	5 hr/month

Table 2-2. Graduate Student Members of the NiteOwl Submission Team

Graduate Team Member	College/Department	Responsibilities
J.K. Chan	Commerce	Work breakdown, budget, management plan
J.E. Giesbrecht	Electrical Engineering	Electronics, detectors, GPS, telemetry
D.P. Harris	Commerce	Work breakdown, budget, management plan
M. Huber	Physics & Engineering Physics	Optical filters and lenses, ozone
E.B. McDougall	Physics & Engineering Physics	Gratings, electronics
J.J. Offiong	Physics & Engineering Physics	Stellar spectra, risk and reliability
J.A. Steele	Mechanical Engineering	Stellar distribution, tomography
M.M. White	Physics & Engineering Physics	Cross-sections, refraction, other species

J. K. Chan holds a B.E. in Electrical Engineering and a B.Sc. in Computer Science from the University of Saskatchewan. He is currently in his final year in the MBA Program in the College of Commerce.

J. E. Giesbrecht holds a B.Sc. in Computer Science, a B.E. in Electrical Engineering, and an M.Sc. in Electrical Engineering from the University of Saskatchewan. In 1995 he was admitted to the Association of Professional Engineers of Saskatchewan as a Professional Engineer (P.Eng). He has extensive research and development experience in non-contact instrumentation, analog and digital electronics, digital signal processing, and database construction. He is currently a Ph.D. candidate in Electrical Engineering with research interests in non-contact measurement of moisture in potash.

D. P. Harris holds an B.Sc. (Hons.) in Physics and an M.Sc. in Upper Atmospheric Physics, both from tbe University of Saskatchewan. He is currently in his final year in the MBA Program in the College of Commerce.

E. B. McDougall holds a B.Sc. (Dist.) in Engineering Physics from the University of Saskatchewan, and is currently completing an M.Sc. thesis, on the feasibility of measuring vertical profiles of minor constituents in the Earth's atmosphere using ground-based incoherent spectroscopy at 150-1200 GHz, in the Department of Physics and Engineering Physics.

M. M. White holds a B.E. in Engineering Physics from the University of Saskatchewan, and is currently an M.Sc. candidate, with a research project on the determination of ozone profiles, temperature recovery methods and the ring effect using the O2 Atmospheric band.

References

Craig, I.J.D. and J.C. Brown, Inverse Problems in Astronomy: a Guide to Inversion Strategies for Remotely Sensed Data, Adam Hilger, Bristol, England, 1986.

Dolovich, A.T., Wang, Z., and Gladwell, G.M.L., An iterative approach to curved ray reconstruction of birefringent fields, Optics and Lasers in Engineering, 22, 347-372, 1995.

Dolovich, A.T., and Gladwell, G.M.L., Convergence criteria for iterative schemes in holographic interferometry and the tomography of strongly refracting objects, Applied Optics, 28, 4411-4418, 1989.

Dubovikova, E.A. and M.S. Dubovikov, Regularization, Experimental Errors, and Accuracy Estimation in Tomography and Interferometry, J. Opt. Soc. Am. A, 4, 2033-2038, 1987.

Hilsenrath, E., and P.T. Kirschner, Recent assessment of the performance and accuracy of a chemiluminescent rocket sonde for upper atmospheric ozone measurements, Rev. Sci. Instrum, 51, 1381-1389, 1980

Kyrölä, E., E. Sihvola, Y. Kotivuori, M. Tikka, T.Tuomi, and H. Haario, Inverse theory for occultation measurements. 1. Spectral inversion, J. Geophys. Res., 98, 7367-7381, 1993.

Lira, I.H. and Vest, C.M., Refraction correction in holographic interferometry and tomography of transparent objects, Applied Optics, 26, 3919-3928, 1987.

McDade, I.C., and E.J. Llewellyn, Satellite Airglow Limb Tomography: Methods for Recovering Structured Emission Rates in the Mesospheric Airglow Layer, Canadian Journal of Physics, 71, 552-563, 1993.

Vest, C.M., Interferometry of strongly refracting axisymmetric phase objects, Applied Optics, 14, 1601-1606, 1975.

Allen, C. W., Astrophysical Quantities, University of London: The Athlone Press, London, 1963.

Bertaux, J. L., G. Mégie, T. Widemann, E. Chassefière, R. Pellinen, E. Kryola, S. Korpela, and P. Simon, Monitoring of Ozone Trend by Stellar Occulations: The GOMOS Instrument, Adv. Space Res., 11, No. 3, pp(3)237-(3)242, 1991.

Brasseur, G., S. Solomon, Aeronomy of the Middle Atmosphere, D. Reidel Publishing Company, Boston, 1986.

Cebula, R. P., H. Park, and D. F. Heath, Characterization of the NIMBUS-7 SBUV radiometer for the long term measuring of stratospheric ozone, J. Atmos. Oceanic Technol., 5, pp. 215-227, 1988.

DeRudder, A., N. Larsen, X. Tie, G. Brasseur, and C. Granier, Model study of PSC's and their effect on stratospheric ozone: 1. Model, J. Geophys. Res., 101, No D7, pp. 12567-12574, 1996.

Fleig, A. J., D. F. Heath, K. F. Klenk, N. Oslik, K. D. Lee, H. Park, P. K. Bhartia, and D. Gordon, User's Guide for the Solar Backscattered Ultraviolet (SBUV) and the Total Ozone Mapping Spectrometer (TOMS) RUT-S and RUT-T data sets: Octobeer 31, 1978 to November 1, 1980, NASA Ref. Publ., 1112, 1983.

Goede, A. P. H., H. J. M. Aarts, C. van Baren, J. P. Burrows, K. V. Change, R. Hoekstra, E. Hölzle, W. Pitz, W. Schneider, C. Smorenburg, H. Visser, and J. de Vries, SCHIAMACHY Instrument Design, Adv. Space Res., 11, No. 3, pp(3)243-(3)246, 1991.

Goede, A. P. H., P. de Groene, R. W. M. Hoogeveen, J. de Vries, R. J. van der A, C. Smorenburg, and H. Visser, SCHIAMACHY Instrument Development for POEM-1, Adv. Space Res., 14, No. 1, pp(1)17-(1)20, 1994.

Herman, J. R., R. McPeters, R. Stolarski, D. Larko, and R. Hudson, Global Average Ozone Change from November 1978 to May 1990, J. Geophys. Res., 96, No. D9, pp 17297-17305, ***.

10. Kawabata, K., Ogawa, H., Yonekura, Y., Ground-Based Milimmeterwave Measurements of Mesospheric and Stratospheric Ozone Employing an SIS Mixer Receriver, J. Geomag Geoelectr., 46, pp755-770, 1994.

11. Keating, G. M., M. C. Pitts, and D. F. Young, Ozone reference models for the middle atmosphere, Adv. Space Res., 10, No 12, pp. 317-355, 1990.

12. Klenk, K. F., P. K. Bhartia, A. J. Fleig, V. G. Kaveeshwar, R. D. McPeters, and P. M. Smith, Total Ozone determination from the Backscattered Ultraviolet (BUV) Experiment, J. Appl. Meteorol., 121, p. 1672, 1982.

13. Kyrölä, E., E. Sihvola, Y. Kotivuori, M. Tikka, T. Toumi, and H. Haario, Inverse Theory for Occultation Measurements: 1. Spectral Inversion, J. Geophys. Res., 98, No. D4, pp. 7367-7381, 1993.

14. Llewellyn, E. J., W. F. J. Evans, J. C. McConnell, I. C. McDade, B. H. Solheim, R. L. Gattinger, Odin Aeronomy, An Application to NSERC for a Collaborative Special Project Grant, 1995.

15. McDonald, M., Stellar Brewer Project, Polar Science Workshop, Windermere Manor, London, Ontario, 1995.

16. Mishchenko, M. I., A. A. Lacis, B. E. Carlson, and L. D. Travis, Nonsphericity of dust-like tropospheric aerosols: Implications for aerosol remote sensing and climate modelling, Geophys. Res. Lett., 22, No. 9, pp. 1077-1080, 1995.

17. Notholt, J., R. Neuber, O. Schrems, T. v. Clarmann, Stratospheric trace gas concentrations in the arctic polar night derived by FTIR-Spectroscopy with the moon as IR light source, Geophys. Res. Lett., 20, pp 2059-2062, 1993.

18. Russell III, J. M., C. L. Gordley, J. H. Park, S. R. Drayson, W. D. Hesketh, R. J. Cicerone, A. F. Tuck, J. E. Frederick, J. E. Harries, and P. J. Crutzen, The Halogen Occultation Experiment, J. Geophys. Res., 98, No. D6, pp 10777-10797, 1993.

19. Saari, H., Leppelmeier, G. W., Korpela, S., and Hoekstra, R., COALA Summary Description, ESTEC Study RFQ/3.8523/95/NL/CN.

20. Schoeber, M. R., M. Luo, J.E. Rosenfield, An analysis of the Antarctic Halogen Occultation Experiment trace gas observations, J. Geophys. Res., 100, No. D3, pp5159-
5172, 1995.

21. Silbert, M. N., Deployment of a Spin Parachute in the Altitude Region of 260,000 Ft., J. Spacecrafts and Rockets, 20, No. 1, Jan.-Feb. 1983.

22. Tie, X., G. Brasseur, C. Granier, A. DeRudder, and N. Larsen, Model study of PSC's and thier effect on stratospheric ozone: 2. Model Results, J. Geophys. Res., 101, No D7, pp. 12575-12584, 1996.

23. Wang, J., J Gille, P. Bailey, L. Pan, L. Rokke, M. Smith, D. Edwards, J. Drummond, G. Davis, H. Reichle, Measurement of Pollution in the Troposphere (MOPITT) Data Validation Plan, Draft, March 1996.

24. Wayne, R. P., Chemistry of Atmospheres, Clarendon Press, Oxford, Second Edition, 1991.

25. World Meteorological Organization Global Ozone Research and Monitoring Project - Report No. 37, Scientific Assessment of Ozone Depletion: 1994, 1995.

*** The Silbert paper (#20) should be referenced at some point, but I can't find an appropriate spot.

Science Team Addresses

Team Member	Phone Number	Fax Number	E-Mail Address	Postal Address
D.P. Steele	(306) 966-6400	(306) 966-6400	David.Steele@sask.usask.ca	Dept. of Physics and Engineering Physics,

Univ. of Saskatchewan,

116 Science Place,

Saskatoon, SK

S7N 5E2
H.S. Caplan	(306) 966-6404	(306) 966-6400	caplan@skatter.usask.ca
A.V. Koustov	(306) 966-6426	(306) 966-6400	kustov@SKISAS.USask.CA
A.I. Smolyakov	(306) 966-6433	(306) 966-6400	smolyakov@sask.usask.ca
R.J. Bolton	(306) 966-5412	(306) 966-5407	Ron.Bolton@Engr.USask.ca	Dept. of Electrical Engineering,

Univ. of Saskatchewan,

57 Campus Drive,

Saskatoon, SK

S7N 5A9
H.C. Wood	(306) 966-5391	(306) 966-5407	woodh@engr.usask.ca
J.D. Bugg	(306) 966-5469	(306) 966-5427	Jim_Bugg@engr.usask.ca	Dept. of Mechanical Engineering,

Univ. of Saskatchewan,

57 Campus Drive,

Saskatoon, SK

S7N 5A9
A.T. Dolovich	(306) 966-5468	(306) 966-5427	dolovich@engr.usask.ca
C.E. Soteros	(306) 966-6118	(306) 966-6086	soteros@snoopy.usask.ca	Dept of Mathematics and Statistics,

Univ. of Saskatchewan,

106 Wiggins Road,

Saskatoon, SK

S7N 5E6
R. Srinivasan	(306) 966-6128	(306) 966-6086	raj@snoopy.usask.ca
E.V. Ivanov	(306) 934-7010	(306) 978-2339	eivanov@eagle.wbm.ca	SCI-TEC Instruments Inc.,

1526 Fletcher Road

Saskatoon, SK

S7M 5M1
J.E. Johnston	(306) 934-7010	(306) 978-2339	jeffj@eagle.wbm.ca
D.J. Sniezek	(306) 934-7010	(306) 978-2339	duanes@eagle.wbm.ca