COSMOS - Cerro Tololo Ohio State Multi-Object Spectrograph

COSMOS is a nearly-identical modified version of the OSMOS spectrograph in use on the MDM Hiltner 2.4-m telescope, and adapted for use on the 4-m telescopes at CTIO. The design modifications, fabrication, assembly and testing were a joint effort between Ohio State and NOIRLab.  This instrument was built to provide a modern, high-efficiency spectrograph for the U.S. community that meets many of the scientific needs described in the ReSTAR (Renewing Small Telescope for Astronomical Research) report. 

General Information:

• COSMOS Manual [3] (PDF)
• COSMOS Fact Sheet [4] (PDF)
• COSMOS Contact Information [5]

Observing Information and Tutorials:

• COSMOS Observing Information
  • COSMOS Startup, Shutdown, and Restart Guide [6]
  • COSMOS Observing Guide [7] (PDF Copy [8])
  • COSMOS Dispersers [9]
  • COSMOS Throughput Curves [10]
• COSMOS MOS Mask Design [11]
• Exposure Times and S/N

Calibration Information:

• Comparison Lamp Spectra [12]
• Calibration Exposure Times [13] 
• Spectrophotometric Standards [14]

Data Reduction Guides:

• IRAF Spectroscopy Documents [15]
• Data Reduction Cookbook [16] (courtesy of R. Shaw)

Older Links:

• C/KOSMOS Documentation in Tucson [17]

Last Updated: 09 March 2018 (SDP)

DECam is a high-performance, wide-field CCD imager mounted at the prime focus of the Victor M. Blanco 4m Telescope at CTIO, with 62 science CCDs (60.5 useful) with 520 megapixels and images 3 square degrees (2.2 degree wide) field at 0.263 arcsecond/pixel resolution.  DECam is a facility instrument, available to all users.    DECam was built to carry out the Dark Energy Survey [18] (DES) Project by the DES Collaboration, which finished observations in January 2019.   We can accommodate programs from small to large, and also those with special requirements such as synoptic and target of opportunity.   Most of the programs fit  within a "half night" organization, which provides a better match of program requirements to lunar phase than does whole night scheduling.  Note that observations are taken "classically", with astronomers present at the telescope, although we can also under pre-arranged conditions support remote observing from a permanent and tested remote observing facility.   We do not offer queue observing.    Please do not hesitate to contact us! (decam-help@ctio.noao.edu [19]).

OBSERVING HELP:

• READ THIS! Safety precautions for operating DECam [20]
• The DECam Users Guide [21] -- Here you can find information on how to prepare and execute your observing run. Includes links to the ETC and scripts editor.
• Instrument Characteristics [22] -- focal plane characteristics, pixel orientation, pixel scale distortion map
• NEW! Remote observing with DECam [23]
• Status of DECam CCDs [24]
• Calibration Files [25] -- crosstalk correction and bad pixel masks
• Filter information [26]
• DECam Shutter [27]
• Known Problems [28]
• Frequently Asked Questions [29]
• READ THIS! Target of Opportunity (ToO): You may be requested to observe a ToO
  • ToO Policy [30]
  • CTIO ToO Protocol [31]
  • ToO programs in semester 2021A [32]

DATA:

• Data Handbook [33]: The DECam Chapter of the Data Handbook (chapter 4) contains information not only about the instrument and observing system, but also covers the data format and the processing done by the DECam Community Pipeline and the resulting data products. 
• A Community Pipeline operated by NSF's NOIR Lab processes raw community-time DECam images and calibration frames into single and stacked frames with astrometric and rough photometric solutions.  All data are served from the NOIRLab Astro Data Archive [34]. 
• DES Data Release 1 (DR1) is here [35]
• The DECam Legacy Survey (DECaLS) Data Releases are available here [36]
• The Astro DataLab [37] also hosts both DES DR1 and DECaLS catalogs
• For DES images we serve single-images (i.e. not stacks) as reduced by the DES pipeline, respecting the 12 month proprietary time.  DES only process and releases those images judged to be of survey quality.  Non-survey quality images may still be scientifically useful for some purposes. 
• DES will issue final catalogs after completion of the survey (~2020-2021).
• NEW! A guide for making custom stacked images [38], by F. Valdes

USEFUL LINKS:

• Talks from the DECam Community Science Workshop (Tucson, May 21-22, 2018) are available here  [39]
• DES DR1 paper is available here [40]
• Talks from the DECam Community Science Workshop (Tucson, March 11-13, 2015) are available here [41]
• Seeing the Big Picture - DECam Community Workshop (18-19 August 2011). [42]
• The workshops Precision Astronomy with Fully Depleted CCDs 2013 [43] and 2014 [44] cover much useful technical information on the DECam CCDs. (At least five of the talks from 2013 are available as papers on Arxiv.org: C. Stubbs "Precision Astronomy with Imperfect Fully Depleted CCDs -- An Introduction and a Suggested Lexicon" [45], P. Antilogus et al. "The brighter-fatter effect and pixel correlations in CCD sensors" [46], A. Rasmussen "Pixel area variations in sensors: a novel framework for predicting pixel fidelity and distortion in flat field response" [47], Plazas et al. "Transverse electric fields' effects in the Dark Energy Camera CCDs" [48], Holland et al. "Physics of Fully Depleted CCDs" [49].
• Valdes & Gruendl (2014) [50] paper on the DECam Community Pipeline
• Science papers based on DECam data [51]

IMPORTANT!

• Acknowledgment in papers [52]

NEWS:

• The last image for the Dark Energy Survey (DES) [53] was taken on January 9, 2019!
• Since early 2018 there is new narrow band (Halpha) filter available in DECam. Details here [54]
• DECam Community Science Workshop 2018 [55] held in Tucson, AZ, May 21-22
• 2016 December 29: During this night CCD S30 began working again!!   Since November 2013 when this CCD "failed" it has shown no stars, nothing but streaks.   The fault was proven to be inside the dewar, and was consistemt with losing a clock signal.  However since Dec 29 star images and flats look completely normal. The revival took place sometime between images 604976 and 605314.
• 2016 March 9:  New version of the ETC (v7) [56] is available with correction of an error in the calculation of the CCD read noise contribution to the total S/N. This was affecting mainly short exposures taken with bluer filters in dark conditions.
• 2015 Dec. A new filter, N964, was installed in the DECam system on December 2015. This is a narrow-band filter made by Materion and funded by an international team with P.I. JunXian Wang of the University of Science and Technology, PRC. It is centered at 9640 A with a width of 95 A. The filter is available for use by NOAO and Chilean community scientists with prior authorization from the PI and his team. Please, contact us [19] in advance if your are interested in using it.
• 2015 Apr 2. Communicating DECam Exposures to Ignore to the NOIRLab Community Pipeline [57]
• 2015 March 7. New version (v6) of the ETC [56] with changes in QE, mirror reflectivity and central wavelength of the u filter.
• 2014 September 2. ETC [56] updated to follow the real DECam PSF rather than a Gaussian
• 2014 March 17.   A VR filter, covering 500-760 nm so approximately twice the bandpass of the SDSS filters, has been successfully installed.   Images are still being evaluated, but looks good!   Exposure failures due to the shutter aborting are a thing of the past, with the replacement of a drive motor.   And, the shutter and filter assembly interior axial surfaces have been painted with anti-reflection paint, and image contamination by bright stars just outside the FOV are greatly (factor 100?) attenuated.
• 2013 December 17:  The Blanco dome encoder system has been replaced.  The new tape and reader provide accurate readings of the dome position (to better than one degree) and misalignments of telescope and dome should now be a thing of the past.
• 2013 November 30:  CCD S30 is not working. Unlike the failure of N30 a year ago that was associated with over-illumination, S30 is exhibiting problems with one of its bias voltages.  It is not 100% sure whether the fault is with the CCD or associated electronics, tests are proceeding.  
• 2013 October 28:  ETC updated to correct an incorrect value for the telescope collecting area, and also it now handles all lunar phases

CTIO Contacts

• DECam Instrument Scientist:  Alistair Walker [58]
• Science support:  Tim Abbott [59], Kathy Vivas [60], Alfredo Zenteno [61], Clara Martinez [62]
• CTIO DECam Support Staff for 2020A [63]
• CTIO DECam Support Staff for 2019B [64]
• Support Staff for older semesters [65]

_________________________________________________________________

CTIO DECam Support Pages [66] (Internal Use Only)

DECam PropIDs & Special Cases [67] (Internal Use Only)

DECam Log of Configuration Changes and Events [68] (Internal Use Only)