Marathon selection process for the INTEGRAL mission
23 May 2001Given the exceptionally high over-subscription to the first INTEGRAL call for observation proposals, the mission's Time Allocation Committee (TAC) faced a daunting task when it met between 14-18 May to start the selection process.
The 291 submissions represented 19 times the total guest-observer allocation during the first year of operation of ESA's gamma-ray observatory. Hard choices faced the 28 top experts during their week-long meeting in Noordwijk, the Netherlands.
The Committee was chaired by Professor Edward van den Heuvel, Director of the Astronomical Institute at the University of Amsterdam. "It was an enormous challenge, not just with the oversubscription but also because of the overall high quality of the proposals," says Professor van den Heuvel.
The TAC members (from 10 different ESA Member States, Russia and the United States) spent the first four days locked in lengthy panel meetings, devoted to four broad domains of gamma-ray astronomy: compact objects (such as black hole candidates, neutron stars, pulsars), extragalactic objects (principally active galactic nuclei, different kinds of galaxies and clusters of galaxies), nucleosynthesis (including supernova remnants, diffuse emission and interstellar phenomenon) and miscellaneous topics, which included gamma-ray bursts.
In each category, the submissions were considered in the light of essential issues such as whether the proposed observation could only be carried out with INTEGRAL, its scientific importance and originality, the soundness of its scientific arguments, the gamma-ray intensity of the proposed target and the consequent likelihood of a successful observation and, the understanding of how INTEGRAL's instruments function.
After initial comments offered by two referees, the panel members - like teachers facing stacks of examination papers - red-lined and dissected each submission. Representatives of the INTEGRAL Science Operations Centre also gave their view on the technical feasibility of each proposal.
During the discussions, there were often intense and lively debates for and against a proposal. Sometimes panel members were sidetracked into expounding their personal scientific views about the target. The panel chairmen had to harness this overflow of enthusiasm, constantly watching the clock to keep to the schedule.
It was a marathon exercise. "Most of the panels averaged 10-15 hours of work each day, and as the end drew near we were burning the midnight oil to get through the remaining proposals," says one committee member.
The concern for absolute fairness in this selection process required that panel members who were themselves associated with proposals under consideration were asked to temporarily leave the room.
On the final day, the four panel chairmen summed up their recommendations in a meeting with Professor van den Heuvel and INTEGRAL project scientist Chris Winkler. All observation proposals were ranked in order of priority - 'A: excellent, must be executed', 'B: good, should be executed' , 'C: do-able, not rejected'. Those which did not fit into the above grades were rejected.
"We set out to go down from the factor 19 oversubscription to something like 2 or 3 which we have to retain as a margin for scheduling reasons," explains Chris Winkler. "The TAC has examined everything but we are far from having finished. It is clear, and a great pity, that some accepted proposals may not be done during AO-1 (the first year of observations), but we still have to see how much we can amalgamate, or if we can combine different proposals which share targets in their fields of view. Furthermore, A and B grade proposals can be transferred to AO-2 if they can't be scheduled in AO-1."
Professor van den Heuvel commented on another important aspect of the selection process: "We also have to achieve a balance between the different scientific interests, such as between nucleosynthesis and the study of compact objects, and between long and short observations. A lot of bargaining lies ahead."
The INTEGRAL Time Allocation Committee will meet again in a few weeks to draw up a first version of a possible guest-observation programme. Further amalgamations and consolidations will follow before final recommendations are submitted to ESA's Director of Science. The definitive list of approved observations is scheduled to be announced this summer.
For more information please contact:
ESA Science Programme Communication Service
Tel: +31 71 5653183