OSIRIS imaging system

OSIRIS (the Optical, Spectroscopic, and Infrared Remote Imaging System) is the main imaging system on Rosetta. The programme started in 1994. At this time Nick Thomas was still working at the Max-Planck-Institut für Aeronomie (now MPS) and participated in the definition of the instrument including the required scientific performance. 

The system comprises two separate optical systems (a narrow angle camera, NAC, and a wide-angle camera, WAC) which are driven through a common electronics box. Several elements of the two cameras are duplicates of each other. For example, the filter wheels, the mechanical shutters, and the focal planes are identical.

The NAC has a pixel scale of around 18.6 urad/px with a point-spread function of around 1.2 pixels (FWHM) (resolution up to 0.17 m/px). The resolution of the WAC is around five times lower, but with a much larger field of view. The NAC contains a series of moderately wide-band filters (typically 60 nm bandpass) designed to provide high-spatial resolution colours of the surface. The WAC contains a series of filters designed to isolate optical gas emissions with a set of continuum filters available to study the dust and its contamination of signal in the gas lines.

UBE Participation in Planning

As co-investigators on OSIRIS, we were supporting MPS by participating in the planning process. The Rosetta activities at the comet are separated into distinct phases (e.g. lander phase, escort phase, etc.). Within the escort phase, there were several 'fly-bys' where the spacecraft passed very close to the surface for a short time. These fly-bys were done to give us information on the structure of the surface and its evolution as the comet moves towards perihelion. Furthermore, the in-situ instruments (e.g. the mass spectrometer, ROSINA) obtained the highest densities of gas and dust during these fly-bys leading to increased signal to noise and also the likelihood of stronger constraint in inhomogeneous outgassing.

The OSIRIS instrument acquired a stunning set of images (Fig. 1) that are available on the MPS website.

Figure 1: Anaglyph prepared by our group and issued as a press release by ESA.

UBE Participation in the Data Analysis

We have analysed a large set of the images acquired (more than 60000 images) and we are still working on it. The main data analysis we have performed are:

- Definition of major regions on the comet ( El-Maarry et al., 2015a; 2016, Thomas et al., 2015)
- Identification of major surface features and surface evolution of comets ( El-Maarry et al., 2015b; 2018, Giacomini et al., 2016, Sunshine et al., 2016, Thomas et al., 2015a; 2015b)
- Identification of water ice at the surface (Pommerol et al., 2015)
- Assessments of gas and dust emission (Marschall et al., 2016; 2017, Gerig et al. 2018).
 
For more information regarding the cometary Science done with Rosetta go to DRAG and LAPIS
 

The Hardware Team

Six scientific institutes are represented in the OSIRIS consortium. Each institute assigned a lead scientist to represent them.  The institutes and lead scientists at the start of the project were 

Max-Planck-Institut fuer Aeronomie (MPAE), Germany (PI: H.U. Keller; replaced by H. Sierks) 
Laboratoire d'Astronomie Spatiale (LAS), France (P. Lamy; L. Jorda) 
University of Padova (UPD), Italy (C. Barbieri) 
Institute for Astrophysics, Granada (IAA), Spain (R. Rodrigo) 
Astronomical Observatory, Uppsala (AOU), Sweden (H. Rickman; B. Davidsson) 
ESTEC (SSD), ESA (K.P. Wenzel; D. Koschny)
 
 

Publications

Bertini, I., N. Thomas, and C. Barbieri, (2004),Modelling of the structure and light scattering of individual dust particles, ASSL Vol. 311: The New Rosetta Targets. Observations, Simulations and Instrument Performances, 167.
 
El-Maarry, M.R., Thomas, N., Giacomini, L., et al. (2015a). Regional surface morphology of comet 67P/Churyumov-Gerasimenko from Rosetta/OSIRIS images. Astronomy and Astrophysics, 583, A26.
 
El-Maarry, M.R., Thomas, N., Gracia-Berná, A., et al. (2015b). Fractures on comet 67P/Churyumov-Gerasimenko observed by Rosetta/OSIRIS. Geophysical Research Letters, 42(13), 5170-5178.
 
El-Maarry, M.R., Thomas, N., Gracia-Berná, A., et al. (2016). Regional surface morphology of comet 67P/Churyumov-Gerasimenko from Rosetta/OSIRIS images: The southern hemisphere. Astronomy and Astrophysics, 593, A110.
 
El-Maarry, M.R., Groussin, O., Thomas, N., et al. (2018). Surface changes on comet 67P/Churyumov-Gerasimenko suggest a more active past. Science.
 
Finklenburg, S., N. Thomas, J. Knollenberg, and E. Kührt, (2011), Comparison of DSMC and Euler Equations Solutions for Inhomogeneous Sources on Comets, 27th International Symposium on Rarefied Gas Dynamics, 2010 AIP Conf. Proc. 1333, 1151-1156, doi: 10.1063/1.3562799.
 
Finklenburg, S. and N. Thomas, (2014) Relating in situ gas measurements to the surface outgassing properties of cometary nuclei, Planetary and Space Science, accepted, 11 February 2014.
 
Finklenburg, S., N. Thomas, C.C. Su , and J.-S. Wu, (2014), The spatial distribution of water in the inner coma of comet 9P/Tempel 1: Comparison between models and observations, Icarus, revised, 31 January 2014.
 
Giacomini, L., Massironi, M., El-Maarry, M.R., et al. (2016). Geologic mapping of the Comet 67P/Churyumov–Gerasimenko's Northern hemisphere. MNRAS, 462, S352-S367.
 
Ho, T.-M. (2005) PhD thesis. University of Berne, Switzerland.
 
Pommerol, A., Thomas, N., El-Maary, M.R., et al. (2015). OSIRIS observations of meter-sized exposures of H2O ice at the surface of 67P/Churyumov-Gerasimenko and interpretation using laboratory experiments. Astronomy and Astrophysics, 583, A25.
 
Sunshine, J., Thomas, N., El-Maarry, M.R. (2016). Evidence for geologic processes on comets. Journal of Geophysical Research: Planets, 121(11), 2194-2210.
 
Thomas, N., Keller, H.U., Arijs, E., et al. (1998). Osiris - The optical, spectroscopic and infrared remote imaging system for the Rosetta orbiter. Advances in Space Research, 21(11), 1505-1515.
 
Thomas, N. (2009) The nuclei of Jupiter family comets: A critical review of our present knowledge, Planetary and Space Science, 57, 1106-1117. 
 
Thomas, N., Sierks, H., Barbieri, C., et al. (2015a). The morphological diversity of comet 67P/Churyumov-Gerasimenko. Science 347 (6220), 1–6.
 
Thomas, N., Davidsson, B., El-Maarry, M.R. et al., (2015b). Redistribution of particles across the nucleus of comet 67P/Churyumov-Gerasimenko. Astronomy and Astrophysics, 583, A17.