Observing Capabilities
======================

This section summarizes the observing capabilities of the global
gravitational-wave detector network as of early 2019. This as a quick reference
to the anticipated commissioning and observing schedule, sensitivity to
gravitational-wave transients, and sky localization accuracy, as described in
the following external documents:

* White Paper [#WhitePaper]_ on gravitational-wave data analysis and
  astrophysics
* Living Review [#LivingReview]_ on prospects for observing and localizing
  gravitational-wave transients with Advanced LIGO, Advanced Virgo, and
  :term:`KAGRA`
* Working Plan Towards O3 [#WorkingPlanTowardsO3]_

Timeline
--------

The gravitational-wave observing schedules is divided into Observing Runs,
epochs of months to years of operation at fixed sensitivity; down time for
construction and commissioning; and transitional Engineering Runs between
commissioning and observing runs. The long-term observing schedule is shown
below. Since :term:`BNS` mergers are a well-studied class of gravitational-wave
signals, this figure gives the :term:`BNS range` for each observing run.

.. image:: https://media.springernature.com/original/springer-static/image/art%3A10.1007%2Fs41114-018-0012-9/MediaObjects/41114_2018_12_Fig2_HTML.gif
   :alt: Long-term observing schedule

Engineering Run 14 (ER14) started on 2019-03-04. The transition into Observing
Run 3 (O3) occurred on 2019-04-01.

During O3, we expect that three facilities (:term:`LHO`, :term:`LLO`, and
Virgo) will observe for one year. It is possible that the Japanese KAGRA
detector may come online and become part of the international
gravitational-wave network at some point during O3. The near-term observing
schedule is shown below, reproduced from [#WorkingPlanTowardsO3]_.

.. image:: _static/G1801056-v4.png
   :alt: Current observing schedule

Live Status
-----------

There are a handful of public web pages that report live status of the
LIGO/Virgo detectors and alert infrastructure.

*  | **Detector Status Portal**: Daily summary of detector performance.
   | https://www.gw-openscience.org/detector_status/

*  | **GWIStat**: Real-time detector up/down status.
   | https://ldas-jobs.ligo.caltech.edu/~gwistat/gwistat/gwistat.html

*  | **LIGO Data Grid Status**: Live dashboard showing up/down status of the
     detectors and online analyses. Status of the LIGO/Virgo alert pipeline is
     indicated by the "EMFollow" box.
   | http://monitor.ligo.org/gwstatus

Sensitivity and Sky Localization Accuracy
-----------------------------------------

The following O3 projections are adapted from the Living Review
[#LivingReview]_ on prospects for observing and localizing gravitational-wave
transients with Advanced LIGO, Advanced Virgo, and KAGRA. The :term:`BNS range`
and :term:`burst range` (luminosity distance of detectable sources, averaged
over sky position and source orientation) given the detectors' anticipated
sensitivities are listed in the table below.

+-----------+-----------+-----------+
| Detector  | Range (Mpc)           |
|           +-----------+-----------+
|           | BNS       | Burst     |
+===========+===========+===========+
| **LIGO**  | 120–170   | 75–90     |
+-----------+-----------+-----------+
| **Virgo** | 65–85     | 40–50     |
+-----------+-----------+-----------+
| **KAGRA** | 8–25      |           |
+-----------+-----------+-----------+

We expect 1–10 :term:`BNS` events over the course of O3. For BNS events, the
median sky localization accuracy of in terms of the 90% credible area will be
120–180 deg². 12–21% of BNS mergers will be localized to less than 20 deg².

Event Rates
-----------

See the `rates presentation`_ from recent Town Hall meeting for LIGO and
Virgo's most current estimates of astrophysical rates of compact binary mergers.

.. |LRR| replace:: *Living Rev. Rel.*

.. [#WhitePaper]
   LIGO Scientific Collaboration & Virgo Collaboration 2018, *The LSC-Virgo
   White Paper on Gravitational Wave Data Analysis and Astrophysics*, LIGO
   Document T1800058-v1.
   https://dcc.ligo.org/LIGO-T1800058/public

.. [#LivingReview]
   Abbott, B. P., Abbott, R., Abbott, T. D., et al. 2018, |LRR|, 21, 3.
   https://doi.org/10.1007/s41114-018-0012-9

.. [#WorkingPlanTowardsO3]
   LIGO Scientific Collaboration & Virgo Collaboration 2018, *LIGO-Virgo
   Working Plan Towards O3*, LIGO Document G1801056-v4.
   https://dcc.ligo.org/LIGO-G1801056/public

.. _`rates presentation`: https://wiki.gw-astronomy.org/pub/OpenLVEM/TownHallMeetings2018/O3_rates_amsterdam.pdf