EVN Calculator

Observing band & data rate [Mbit/s]
On-source integration time [min]

A simple guide:

- one station: SEFD
- two stations: baseline sensitivity
- more stations: image thermal noise

- field of view and EVN MkIV correlator limitations
are given below

Number of spectral channels per subband, integration time [s], and maximum baseline length
Number of polarizations, subbands per polarizations, and bandwidth of a subband [MHz]

Please select an array (N>2) and an observing band.

MkIV Correlator limitations no longer apply.

A couple of comments:

- The following link describes using JVLA as a VLBI station.
- The MkIV correlator limitations no longer apply.
All projects including e-VLBI are now correlated with the EVN Software Correlator (SFXC)
- Your datarate [Mbit/s] = bandwidth/polarization [MHz] * Npol * Nbit (1 or 2 bit sampling) * 2.
- See (an old) list of the two-letter station codes.
- VLA: phased array; your target source will probably contribute significantly to the noise.
For arrays including the VLA, or any of the big dishes (like Arecibo, Effelsberg, Lovell Telescope,
Westerbork etc.) the above noise estimates are realistic only for weak target sources.
- For bright sources (~Jy) dynamic range limitations dominate, not the thermal noise.
- Some stations have only 1 polarization, this is not included here (see the EVN Status Tables)
- Not all stations can record at 512 and 1024 Mbit/s, this is not checked in the calculator.
- The noise is higher for globals if VLBA and EVN observes together only in a limited timerange.
- Only zenith SEFDs used, no gaincurve corrections applied. The 3mm SEFDs are given assuming
typical weather conditions and a mean elevation of 30 degrees (see note below).
- The formula for calculating the thermal noise is below (the VLBI efficiency factor eta is 0.7):

- If some stations are present for only part of the observation the sensitivities can be calculated for
each portion of the observation and combined as follows:

For example to calculate the sensitvity of a C band, 512Mb/s global experiment, 6 hours in duration
which includes Arecibo for 2.5 hours.

3.5 hours global = 8.018 uJy/beam
2.5 hours global + Ar = 4.679 uJy/beam

Combined sensitivity:

Recent changes:

- Added 8, 4, 2, 1-spectral channel cases to FoV calculation - useful when spectral channels within subbands are partially or fully averaged in post-processing. 16 Jan 2021

- Removed Arecibo (temporarily?) on 4 Jan 2021

- Removed 22 GHz for Sheshan 25m on 2 Feb 2016 (receiver too old, will not be replaced)

- Added ALMA (37 telescopes available for VLBI) on 28 Jan 2016 (replacing TIGO - Tc in the calculator)

- Updated JVLA SEFDs and added Ka band (30 GHz) on 30 June 2015

- Added the Tianma, the new 65m dish in Shanghai (Tm65) and removed Simeiz (Sm) on 17 September 2014.

- Added 64 and 128 MHz suband bandwidth, available on RDBEs with DDC personality on 28 July 2014.

- Updated VLBA SEFDs based on the latest VLBA Observational Status Summmary performance table on 21 May 2014.

- Updated GMVA 3mm SEFDs based on the GMVA webpage and e-mails from Thomas Krichbaum on 2013 July 23.

- Added KVN stations Ku-Ulsan, Ky-Yonsei, Kt-Tamna (note X-band SEFDs are expected values);
added LBA stations ATCA, Mopra, Hobart, Ceduna, ASKAP (Ap-no official 2-letter code yet)
updated VLBA 6cm-5cm SEFDs; added Torun K-band, Yebes40m 3mm; finer spectral
resolution and time averaging is now possible (8192 ch/15 ms int.) - on 2 July 2013.

- Added Noto to the e-EVN array on 18 May 2012.

- Added 2048 Mbps mode on 6 Jan. 2012 (becoming available at the VLBA).

- Updated SEFDs on 19 Sep. 2011 based on the EVN status table for several telescopes.

- Added Sardinia-Sr with expected SEFDs on 1 Feb 2011; note Sr is not available yet. Ys SEFDs updated.

- Miyun-My, Kunming-Km in China, Svetloe-Sv, Zelenchukskaya-Zc, and Badary-Bd in Russia added on 12 Jan 2010.
SEFDs will be updated as they become available.

Comments/suggestions to
Zsolt Paragi