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SAGENAP says DES science program "truly excellent"

The SAGENAP report is out in draft form, and it says "The science program proposed by DES... is truly excellent." and that "A strength of this project is that it can combine the experience of a DOE high energy physics laboratory with the astronomical community at a major astronomical observatory. " The full description is below.
2.3.1. Dark Energy Survey (DES)

The Dark Energy Survey (DES) plans a 5000 deg2 survey down to 24th magnitude brightness levels with the goal of measuring w, the vacuum energy equation of state. The survey would be done in four wavelength bands using a new 3 deg2 camera on the Blanco 4m telescope at Cerro Tololo in Chile. The DES proponents envision a fouryear construction schedule, followed by four years of observations.

The science program proposed by DES, consisting of weak lensing, cluster photometric redshifts, and Type Ia supernovae, is truly excellent. We find many positive features to commend the project. Especially noteworthy is their estimate that the SZ catalog of 30,000 galaxy clusters from the South Pole Telescope (SPT) could be used to measure w to a precision approaching that of the SN Ia projects. This would be an important independent measurement of one of the most critical quantities in cosmology with very different systematic errors from measurements made of Type Ia supernovae. Such a measurement is an essential ingredient of any systematic study of the vacuum energy. There was no discussion of the capabilities of DES to probe w'.

While the science goals of the project are excellent, SAGENAP has concern that the project might be substantially more expensive than estimated by the team. The team discussed the challenge posed by the detectors and the optics. Both aspects must be well understood in order for DES to achieve its scientific goals in a timely way. The optical performance of the system is crucial to making good weak-lensing measurements from the ground. The requirements on the stability of the system could prove to be a significant challenge.

The plan to acquire ten times the data of the Sloan Digital Sky Survey (SDSS), but spend substantially less on computing than SDSS, was a concern noted by several sub-panel members, although offsetting this concern is that DES can build on the SDSS software base and utilize the significant advances in hardware that have become available over the last few years. Nonetheless, the data acquisition and processing will be a significant challenge. In addition, although the Fermilab team proposing to build the 10 camera has a strong record with silicon vertex detectors, it may need more experience in astronomical instrument development and use.

A strength of this project is that it can combine the experience of a DOE high energy physics laboratory with the astronomical community at a major astronomical observatory. This type of collaboration was seen as an excellent match for this kind of science and the sub-panel felt that it should be encouraged. The details of the operational arrangement between the lab and the observatory will need to be better defined.

In summary, the DES project has considerable scientific merit, and the team appears to be strong and well focused. Questions regarding the real cost (particularly related to software) and the place of DES in an overall multi-agency initiative on dark energy remain unclear. A Dark Energy Roadmap would provide the needed context for this project (and others exploring dark energy).
Created by annis
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Last modified 2005-04-18 10:46 AM

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