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S. Ott,1 A. Abergel,2
B. Altieri,1
J-L. Augueres,3 H. Aussel,3
J-P. Bernard,2 A. Biviano,1,4
J. Blommaert,1 O. Boulade,3
F. Boulanger,2 C. Cesarsky,5
D. A. Cesarsky,2 A. Claret,3
C. Delattre,3 M. Delaney,1,6
T. Deschamps,3
F-X. Desert,2 P. Didelon,3
D. Elbaz,3 P. Gallais,1,3
R. Gastaud,3 S. Guest,1,7
G. Helou,8 M. Kong,8
F. Lacombe,9 J. Li,8 D. Landriu,3
L. Metcalfe,1 K. Okumura,1
M. Perault,2 A. M. T. Pollock,1
D. Rouan,9 J. Sam-Lone,3
M. Sauvage,3 R. Siebenmorgen,1
J-L. Starck,3 D. Tran,3
D. Van Buren,7 L. Vigroux,3 and
F. Vivares2
1ISO Science Operations Centre, Astrophysics Division
of ESA, Villafranca del Castillo, Spain
2IAS, CNRS, University of Paris Sud, Orsay, France
3CEA, DSM/DAPNIA, CE-Saclay, Gif-sur-Yvette, France
4Istituto TESRE, CNR, Bologna, Italy
5CEA, DSM, CE-Saclay, Gif-sur-Yvette, France
6UCD, Belfield, Dublin, Ireland
7RAL, Chilton, Didcot, Oxon, England
8IPAC, JPL and Caltech, Pasadena, CA, USA
9DESPA, Observatoire de Paris, Meudon, France
ESA's Infrared Space Observatory ( ISO) was successfully launched on November
17th, 1995.
ISO is a three-axis-stabilised
satellite with a 60-cm diameter primary mirror (Kessler et al. 1996; Maldari
et al. 1996). Its four instruments (a camera, ISOCAM, an imaging
photo-polarimeter, and two spectrometers) operate at wavelengths
2.5-240µm at temperatures of 2-8K.
ISOCAM takes images of the sky in the wavelength range 2.5-18µm (Cesarsky et al. 1996). It features two independent 32×32 pixel detectors: the short-wavelength channel (2.5-5.5µm), and the long-wavelength channel (4-18µm). A multitude of filters and lenses enable the observer to perform measurements at different wavelengths, with different fields of view or polarizers.
The requirements on CIA were, in decreasing order of importance:
External constraints were the extremely tight schedule (see § 4) and the operating system. For historical reasons, VAX/VMS was chosen as operating system for the pipeline. It was also decided that data files within the processing environment be in a VAX-specific variant of FITS. Therefore, in order to stay as close as possible to the ISOCAM pipeline, the operational CIA version had to run under VMS. To achieve sufficient performance, it was decided to opt for VMS/Alpha instead of a classical VAX operating system, and accept the minor porting efforts required.
Given the time constraints and the team-structure, it was decided to re-use the existing IDL experience and code as much as possible. Therefore IDL (V3.6) and high level languages (C, C++) for special IA applications and FORTRAN (programming language for the pipeline) were chosen.
In order to be able to meet the schedule, it was decided to break the development down into three steps: a mimimum system, covering requirements 1-4; an operational system, covering requirements 1-6; and the final astronomical data-processing system, covering all requirements listed in the previous section. The core system was intended for expert users, having only a very limited use of graphical user interfaces for display purposes.
Standardized module headers were designed to provide help to the users. Their contents feed into
For the full astronomical data-processing system, a UNIX version tuned to the needs of astronomers was introduced, together with more user-friendly, widget-based applications.
The development of CIA began in June 1994 and followed standard software engineering practice (ESA PSS-05). User requirements were consolidated in September 1994 and the first version of the architectural design document agreed in November 1994. The minimum system was completed to meet the target date for IA readiness in April 1995, and the operational system in November 1995 prior to the launch of ISO. Since then, work has continued for the astronomical data-processing system, the next version is expected to be released in December 1996.
Currently, the system is comprised of over 1000 IDL modules totalling over 210,000 lines, around 200 FORTRAN files taken from the pipeline processing system, and around 10 FORTRAN, C, and C++ files for specialized (mainly cpu-intensive) applications.
Around 15 man-years have been spent in the development of the IA core system, excluding the time for algorithmic research. For comparison, 30 man-years went into the calibration of ISOCAM and 5 man-years into ISOCAM related pipeline processing. This amounts to around 3% of the overall cost of ISO Science operations or 0.4% of the total ISO cost to completion.
A quasi-object-oriented approach was taken, with functions communicating via standardized data structures. The same data structures are used by the pipeline, calibration procedures, and astronomical data analysis. This commonality improves considerably the speed of algorithmic development within CIA.
Figure: Data Flow and Architecture.
Original PostScript figure (5kB).
SCDs, CDSs and SADs are implemented as complex IDL data structures using pointers and therefore need dedicated access functions.
Cesarsky, C., et al. 1996, A&A, 315, 32
Delaney, M. ed., ISOCAM Interactive Analysis User's Manual, ESA Document
ESA Software Engineering Standards, ESA Document, Reference PSS-05
Kessler, M., et al. 1996, A&A, 315, 27
Maldari, P., Riedinger, J., & Estaria, P. 1996, ESA Bulletin, number 86
Siebenmorgen, R., et al. ISOCAM Data User's Manual, ESA Document, Reference SAI/95-221/DC
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