OSIRIS on Odin

The Canadian designed and build Optical Spectrograph and InfraRed Imaging System (OSIRIS), is deployed and currently in operation aboard the Swedish Odin satellite.

OSIRIS measures vertical profiles of spectrally dispersed, limb scattered sunlight from the upper troposphere into the lower mesosphere and was launched February 2001 into a sun-synchronous, 6 pm / 6 am local time orbit at 600 km. This restricts OSIRIS sunlit observations to the Northern hemisphere in May, June, July August and the Southern hemisphere in November, December, January and February. Global coverage from 82°S to 82°N occurs on the months adjoining the equinoxes. OSIRIS measurements began November, 2001 and continue to the present. OSIRIS remains fully operational and processing of its data algorithm will be maintained into the foreseeable future.

Objectives

The objective of the Odin mission is to provide new information on the extent to which humans are changing the atmospheric environment, specifically through the study of stratospheric and mesospheric ozone, and the coupling and energy budget of these regions.

Stratospheric ozone science: To elucidate the geographical extent of, and mechanisms responsible for, ozone depletion in the “ozone hole” region and to study dilution effects and possible heterogeneous chemistry even outside of the polar regions due to sulphate aerosols.

Coupling of atmospheric regions: To study some of the mechanisms that provide coupling between the upper and lower atmosphere, e.g., downward transport of NO with its effects on ozone photochemistry and the vertical exchange of minor species such as odd oxygen, CO, and H2O.

Instrument

The OSIRIS spectrograph measures from 274 nm to 810 nm with a single line of sight that is scanned through a range of tangent altitudes. Each scan typically ranges from 7 km to 65 km and takes 40 seconds to acquire. The measurements are used to produce height profiles of O3, NO2, and stratospheric aerosols.

The Odin satellite was operated until June 2007 as a joint mission between astronomy and aeronomy disciplines. 50% of the total observation time was dedicated to each discipline where time was split into 1 day segments. Odin has operated as a purely aeronomy mission since June, 2007, and continues to the present, with almost complete coverage.

OSIRIS is a Canadian instrument, operated by the Canadian Space Agency. The mission PI is Dr. Doug Degenstein and Co-Investigator, Dr. Adam Bourassa both at the University of Saskatchewan. Odin is operated by the Swedish Space Corporation, with funds from the European Space Agency as a Third Party Mission.

OSIRIS Level 1 Services

The OSIRIS Level 1 Services provides a Python interface to the OSIRIS Level 1 data products. This API, which replaces the C++ version originally developed in the late 1990’s, requires your machine to have access to a copy of the Level 1 data products which is often prohibitive for many end users not located on the University of Saskatchewan campus. If you would like more information on how to access the OSIRIS Level 1 data, please contact Chris Roth

OSIRIS Level 2 Data Products

The OSIRIS spectra of limb scattered sunlight are used to retrieve the ozone number density vertical profiles over the altitude range from 10 to 60 km at a vertical resolution of approximately 1.5 km using the SaskMART Multiplicative Algebraic Reconstruction Technique, which is a one dimensional modification of a two-dimensional tomographic retrieval algorithm. This technique allows for the consistent merging of the absorption information from radiance measurements at wavelengths in the Chappuis and the Hartley-Huggins bands at each iteration of the inversion. A set of weighting factors is used to determine the importance of each line of sight and each element of the measurement vector for the retrieved state at each altitude. OSIRIS ozone profile measurements show agreement with coincident SAGE II occultation measurements to within 2% from 18 to 53 km altitude over a large range of geolocations and solar zenith angles.

Vertical profiles of stratospheric aerosol extinction at 750 nm are also retrieved using OSIRIS limb scattered sunlight. All the spectra obtained with a single vertical scan of the spectrograph line of sight are used together to retrieve an extinction profile with approximately 1.5 km vertical resolution. A wavelength ratio of 750 nm to 470 nm is used to characterize the effect of the Mie scattering signal. Hydrated sulphuric acid particle microphysics, including a size distribution for typical background aerosol, are assumed to calculate the scattering cross section and phase functions required to retrieve the aerosol extinction.

Both data products are regularly processed at the University of Saskatchewan for OSIRIS stratospheric limb scan measurements. Data from November, 2001, to the current date is available for download as an OSIRIS Level 2 Product. The data products are governed by ESA data distribution guidelines. We request that users contact the algorithm lead developers Doug Degenstein and/or Dr. Adam Bourassa if they intend to publish or make extensive use of these products.

Download

The OSIRIS level 2 data are available at our ftp server and require the following username and password:

  • u: osirislevel2user
  • p: hugin

ESA asks that you use the data free of charge and obligation once you have completed a registration form outlining your area of research, etc. ESA keeps track of the number of registered users and uses this information to justify continued funding of the Odin mission. ESA funds the Odin satellite as a 3rd party mission and they ask that all data users be registered with them. Unfortunately the process uses a standard form for all 3rd party missions which by itself is harmless, except they ask questions that unsettle many people. As an OSIRIS data user you are not required to provide any yearly reports of any kind to ESA even though the application forms asks you to agree to this after your application is submitted.

If you are having trouble locating the data you are interested in, contact Chris Roth.