According to the H.E.S.S. MoU, external proposals from outside the H.E.S.S. collaboration will be considered along with internal proposals, to the extent that they add new aspects beyond the physics program and the lists of candidate sources discussed and documented by the H.E.S.S. physics working groups. Up to 150 scheduled observation hours per year are available in this mode.

Proposal submission: Proposals should be addressed to the secretary of the H.E.S.S. Observation Committee (E-Mail 1 or E-Mail 2). It is suggested that proposers contact the chair of the relevant H.E.S.S. physics working group to check if the object has already been observed or is on the H.E.S.S. target list. The H.E.S.S. observation program is usually defined each fall for the coming year, and proposals for the next year should normally be submitted by October 1. Typical observation times for initial observations of new targets are 10 h to at most 20 h.

Data analysis: H.E.S.S. cannot, at this time, provide analysis tools for non-experts. We suggest that data analysis be carried out in cooperation with H.E.S.S. groups. H.E.S.S. institutes may also host external scientists working on data analysis. Arrangements concerning data analysis and authorship on possible publications should normally be clarified beforehand and stated in the proposal.

Data rights are granted to the proposers for one year after data are available in Europe. After this time, the H.E.S.S. collaboration on its own may decide to publish results based on the data.

Multiwavelength campaigns. Information about planned multiwavelength campaigns is given on the HESS Multi-wavelength Working Group homepage.

Proposal tools and information about the instrument

• Tool to evaluate observation windows and zenith angle ranges
• Energy threshold: for “normal” analysis, the nominal post-cuts energy threshold is 0.16 TeV at zenith, 0.22 TeV at 30 degr. zenith, 0.40 TeV at 45 degr. and 1.2 TeV at 60 degr. See Aharonian et al. 2006 (Table 3 and Fig. 14) for more details and other analyses cuts. Depending on the state of telescope mirrors, actual thresholds may be somewhat higher.
• Sensitivity: about 1% of the Crab flux for 25 h or observations near zenith, for point sources. Sensitivity degrades with increasing zenith angle, and is significantly reduced beyond 45 degr. zenith angle. See Aharonian et al. 2006 (Fig. 21) for more information about sensitivity. The differential flux sensitivity near zenith is shown here, given is the minimal detectable flux per bin of width 0.2 in log10(E), for a 5 sigma signal or 10 events in 25 h. For extended sources, sensitivity degrades roughly by a factor (theta/0.15 degr) where theta is the radius of the on-source region.
• Field of view: Sensitivity is flat out to ~1 degr. from the telescope axis and drops to ~40% at 2 degr. See Aharonian et al. 2006 (Fig. 8).
• Angular resolution: typically 0.1 degr. for individual photons, better for selected subsets, see Aharonian et al 2005 (Fig. 2) for details. The effective pointing precision, relevant for systematic errors on source centroids, is about 20″ in each coordinate.
• Energy resolution: typically 15-20% for individual photons, depending on energy and location in the field of view.
• Observation mode: observations are usually carried out in wobble mode, with the target 0.5-0.7 degr. off axis, using the opposite region for background evaluation. Extended objects may require other observation modes.