The night “Comisión de Asignación de Tiempos” (CAT) evaluates the observing proposals that guarantee to the Spanish community access to the majority of the night telescopes at the “Observatorios de Canarias” (OOCC): GTC, WHT, INT, TNG, NOT, Mercator, and Liverpool on La Palma, and Stella on Tenerife. Likewise, the CAT distributes the time allotted to Spain on the GTC, in the same way that it jointly manages, together with Mexico, the 2.5% of GTC time in collaboration with this international partner.

Telescope time is offered and allocated twice a year in periods of 6 months. Allocation periods run differently depending on the telescope as indicated next: 

*A two month overlap period is adopted at the start and end of each period, when proposals from both semesters may be observed, in order to reduce problems with under-filled observation queues.

The night-time CAT is composed by three panels with five well-known astrophysicists each, one President (that represents the Director of the IAC), and one Vice-President.

There are different schemes to apply for observing time with GTC, WHT, INT, TNG, NOT, Mercator, Liverpool (LT), and Stella: Ordinary proposals (including regular and Large programs), DDT, Service Time, and various international agreements. See "how to submit" section to learn how and when proposals  (of any category: regular, large, service, DDT, …) can be sent to the CAT.

• The IAC80 and Carlos Sánchez Telescope (TCS) are no longer offered through CAT since semester 2013A. Any interested potential users must directly contact the Head of Telescope Operations at the IAC [aoscoz at iac.es], or visit this web site.

Applying for night CAT time

There are different schemes for proposals as indicated below:

• The standard call for proposals: Telescope time for GTC, WHT, INT, TNG, NOT, Mercator, LT, and Stella is allocated twice a year in periods of 6 months. Regular and large proposals are accepted according to the conditions described in the standard call for proposals every semester. Allocation periods run as follows:

*A two month overlap period is adopted at the start and end of each period, when proposals from both semesters may be observed, in order to reduce problems with under-filled observation queues.

• DDT. Up to a few per cent of the general observing time may be used for the IAC Director’s Discretionary Time (DDT) Proposals on GTC, WHT, INT, TNG, and NOT. See DDT GTC and DDT WHT, INT, NOT, TNG for further details on conditions and for application forms. DDT proposals can be submitted at any time.
  • GTC. Approved DDT proposals can be executed in either visitor or queue mode according to the Principal Investigator’s requirement.
  • WHT, INT, TNG, and NOT. The CAT DDT nights are known a priori for each semester. Interested applicants must submit their proposals asking for specific nights ideally 20 days (strict limit is 10 days) before the scheduled CAT DDT nights. DDT proposals are to be executed in visitor mode.
  • INT, TNG, and NOT. DDT proposals are accepted for every night allocated as Service Time. Applicants must indicate in their proposal that they are applying for a DDT program.
• Service Time. A fraction of the general observing time is also offered in the form of Service time on WHT, INT, NOT, LT, and TNG. Service proposals can be submitted at any time (see next), and will be “active” for a period of 1 year.
  • INT, NOT, TNG. The CAT service nights are known a priori for each semester. Interested applicants must submit their proposals asking for specific nights ideally 10 days before the scheduled CAT service nights. Service observations on the INT, NOT, and TNG will always be executed by the team of IAC support astronomers. For the three telescopes, you can find the list of approved CAT service proposals and the list of available CAT DDT and service nights.
  • WHT. The service time is shared by all TACs. Service observations on the WHT are executed by ING staff. WHT service proposals can be submitted at any time.
  • LT. Service mode on the LT (“LT reactive time”) is recently implemented within the CAT (semesters 2016A and 2016B). Observations run in queue mode and are executed by LT staff. No LT reactive time is available in 2017A. 
• Other schemes of proposals are available, such us: IACNordic collaborative time (NOT), Spain-Mexico collaborative time (GTC), International Time Program (ITP), which result from various agreements between Institutions.

Regular and large proposals

Observing time for the telescopes of the “Observatorios de Canarias” (OOCC): GTC, WHT, INT, TNG, NOT, Mercator, and Liverpool on La Palma Island, and Stella on Tenerife, is offered and allocated twice a year in periods of 6 months. Calls for proposals are usually opened at March and September every year. Meetings of the committee usually take place at May and November. Proposals must be submitted using the night time CAT application tool (see below "how to submit proposals" section).

Regular and Large Proposals for all telescopes are accepted at these ordinary calls. Details and limitations for each specific semesters are detailed in the corresponding Call for Proposals. Regular proposals are those whose executation is limited to one semester. 

Large programs are defined as projects with the potential to lead to a major advance in a specific field of astrophysics. They may extend to more than one semester, with a maximum of four semesters. Up to 66% of the time distributed by the CAT on the Liverpool, Mercator, STELLA, and INT, up to 33% of the time on NOT and TNG, and up to 15% of the time on the WHT may be assigned to Large Programs. See the call for proposals of a specific semester for possible limitations in the time available for  Large proposals caused by previously accepted, ongoing projects. In addition to a strong scientific justification, proposers should demonstrate to have the necessary manpower and tools for a quick and comprehensive analysis of the data and publication of the results.

• Large programs on the GTC. These projects should require a minimum of 100 hours that can be distributed over up to four semesters, with a limitation of  100 h per semester. These 100 hours follow the standard division into dark, grey and bright time (50-30-20). This limits the maximum allocation to GTC Large programs per semester to 50 hours in dark time, 80 hours in dark/grey conditions, and 100 hours without any moon restriction. Given these limits, a GTC Large program can request up to a total of 200 hours of dark time distributed over 4 semesters, 320 hours in grey time, and 400 hours with no moon restrictions. Execution of a GTC-LP will be preferentially done in service/queue mode.  Requests to conduct it (partially or completely) in visitor mode will be considered if it significantly improves the efficiency of the proposed observations. Note, however, that payback for bad weather or technical failure in visitor mode will no be offered. As the observing time is deduced from the CAT share, only GTC Large Program applications with PIs and a large part of team from Spanish institutions will be accepted.

• A report on the progress of Large Programs should be submitted to the CAT yearly (all telescopes except for GTC) and every semester for the GTC.

• Proprietary period for Large Programs will be that of the applied telescopes, except for GTC, whose raw data will be public one year after the completion of the GTC Large program. The PI of a GTC Large project will also be asked to put the reduced data into the GTC archive.

Both regular and large proposals should be submitted using the application tool http://cat.iac.es. See below the "how to submit" section for more information.