Observing with APEX

Introduction

APEX is a 12 meter radio telescope built by an international collaboration involving the Max-Planck-Institut für Radioastronomie (MPIfR), Onsala Space Observatory (OSO), and ESO; operations are entrusted to ESO. The observing time is shared as follows: Max Planck Institutes and German universities receive 45%, ESO receives 25%, OSO receives 20% and Chile 10%.

The Annual variation of the Precipitable Water Vapour (PWV) at the APEX site is shown in the figure below.

"Figure 1. Left: Annual variation of the Precipitable Water Vapour (PWV) content at Chajnantor, based on historical observations with the APEX radiometer recorded in the last 9 years. Blue, green and red histograms indicate the 25, 50 and 75 percentile levels, respectively. The yearly APEX science operations period from 20 March till 20 December is scheduled to avoid the worse conditions during Altiplanic winter; Right: Historical cumulative plot showing the fraction of days with PWV contents below a certain value. Only observations collected during the science operations periods are considered in this plot."

Applying for observing time

• APEX instrumentation

  The link above gives a summary of important system parameters for all receivers and backends available at APEX. Currently the following receivers are available:
  Facility receivers: SHeFI (heterodyne, 213-500 GHz & 1250-1384 GHz) and LABOCA (bolometers, 345 GHz).
  PI receivers: FLASH & CHAMP⁺ (heterodyne), only available in collaboration with MPIfR staff; contact Rolf Güsten at MPIfR (rguesten(at)mpifr-bonn.mpg.de) at least two weeks before submitting proposals. SEPIA (heterodyne) Band 5 and Band 9 receivers
  Here are a few important reminders for proposers.

  • SHFI

    • APEX-1

      APEX-1 covers low frequencies, allowing observations during conditions with PWV > 2 mm. Larger proposals for PWV > 2 mm conditions are encouraged.

    • APEX-2

      Observations at these frequencies generally require PWV < 2 mm conditions.

    • APEX-3

      Observations in this frequency range require the best quartile of precipitable water vapour conditions (PWV < 0.5 mm).
    
    Note that the time needed to search for an appropriate off-source position in extended line-emitting regions is not included. SHFI users wishing to map extended line-emitting regions should either provide an appropriate off-source position, or request additional observing time in the technical justification section to search for such a position. The overhead for this amounts to ~30min per field.

  • LABOCA, the Large APEX Bolometer Camera

    The point source photometry mode consists of single pixel chopping which provides more on-source integration time than mapping modes. This, however, makes it more sensitive to unstable weather conditions and instrumental effects. The necessary atmospheric stability typically requires PWV < 1 mm conditions. There are two important additional requirements to use the photometry mode: (1) the positions should be known with an accuracy of <3'', and (2) the sources should not have other emission within the wobbler throw radius.

  • SABOCA, the Submillimetre APEX Bolometer Camera

    Potential users of the SABOCA photometry mode should be aware that a very accurate pointing is essential to use this mode. This generally requires the availability of a bright (S(350 micron) > 1 Jy) pointing source within 10 deg of the targets. In addition, very stable conditions and PWV < 0.5 mm are required.
    During ESO period 92, SABOCA is expected to be available only in September 2013.

  • FLASH, the First Light APEX Submillimeter Heterodyne receiver

    FLASH is a dual-frequency heterodyne receiver, allowing for simultaneous observations in the frequency ranges 272-377 GHz and 385-495 GHz. This is a PI instrument from MPIfR.

  • CHAMP⁺, the Carbon Heterodyne Array of the MPIfR

    CHAMP⁺ is a dual-color heterodyne array for spectroscopy in the 450 and 350 micron atmospheric windows. It provides simultaneous observations with 7 pixels at a given frequency in the range 620-720 GHz, and 7 pixels at another frequency in the range 780-950 GHz. This is a PI instrument from MPIfR.

• APEX Science schedule

  APEX observing science schedule.

• Observing time estimation

  Each proposal must be accompanied by an accurate estimate of the necessary observing time needed to complete the project, based on the required sensitivity and the receiver characteristics.
  The atmospheric transmission at APEX as function of observing frequency and precipitable water vapor can be calculated in the following link .
  There are observing time calculators for LABOCA, SABOCA, SHeFI receivers (ON-OFF) and SHeFI receivers (On The Fly).

• Proposal submission

  • ESO

    ESO proposal deadlines are set up twice a year, in March and September, for the observing periods 1 October - 31 March and 1 April to 30 September, respectively. Please consult the ESO Proposal Preparation and Submission web page for details.
    APEX contact: Carlos de Breuck, email: cdebreuc(at)eso.org

  • Sweden (Onsala Space Observatory, OSO)

    Calls for proposals for swedish time at APEX are announced at OSO's Proposal Guidelines for details.
    APEX contact: Michael Olberg, email: michael.olberg(at)chalmers.se

  • MPIfR

    APEX contact: Rolf Güsten, email: rguesten(at)mpifr-bonn.mpg.de

  • Chile

    Chilean APEX proposal deadlines are set up twice a year, in March and September. Please consult the Conicyt webpage for details.
    APEX contact: Diah Gunawan, email:diah.gunawan(at)uv.cl

Performing observations with APEX

Observations at APEX are normally done in service mode. For questions, please contact the APEX station manager, Thomas Klein, email: tklein(at)eso.org

Once you proposal is accepted, you need to prepare the observations. This basically means you need to inform the APEX staff about everything which is important for carrying out your observations, including source coordinates, receiver setup, possible pointing sources, observing procedures, etc.

• Preparing an observing run

  This page explains what information you have to submit, and provides links to a project submission web form as well as a pointing source search interface.

• APECS User Manual (Revision 3.3, February 12^th, 2017)

Reducing APEX data

The APEX raw data are in the so-called MB-FITS data format. For line observations, these raw data are calibrated on-line by the OnlineCalibrator program, which writes the calibrated spectra (T_A^* scale) into a CLASS-format data file. The data can be further reduced and analyzed using for example CLASS and GRAPHIC or MAPPING program of the GILDAS software package.

Related Links:

• Multi-Beam FITS Raw Data Format - Interface Control Document (pdf)
• APEX Calibration and Data Reduction Manual - by E. Polehampton and H. Hafok (pdf)

APEX End of mission report

Please take some minutes to evaluate your observing mission at APEX using this form. Thanks!