Sensitivities

A. 3mm VLBI detection limits

Here we assume optimum weather conditions (low opacity, tau < 0.1, no clouds).

Important: Depending on weather and elevation, Tsys and SEFD could be considerably higher!

Antenna and Receiver properties at 86 GHz:

Station	Diameter (m)	Tsys (K)	Gain (K/Jy)	Eta (%)	SEFD (Jy)	Comment
GBT	100.0	130.0	0.98	35	133	for nighttime observing
Effelsberg	80.0 (eff.)	140.0	0.14	7.7	1000	-
Noema	46.2 (eff.)	70.0	0.42	70	163	10x15m
Pico Veleta	30.0	100.0	0.15	60	654	-
Yebes	40.0	100.0	0.10	22	990	-
VLBA (8x25m)	25.0	115.0	0.028	16	4100	range is: 0.01-0.04 K/Jy
KVN (3x21m)	21.0	150.0	0.05	40	3000	for each 21m antenna
Onsala	20.0	130.0	0.049	43	2650	-
Metsähovi	14.0	150.0	0.010	18	15000	-
LMT (prelim)	50	200.0	0.39	55	513	double side band
GLT	12	170	0.032	78	5312	-
ALMA	71.1 (eff.)	70.0	1.02	71	69	37x12m

7 sigma single baseline detection thresholds (all numbers in mJy):
link to: EVN Sensitivity calculator1 (classic, please open in new browser window), and EVN Sensitivity calculator2 (new), and GMVA Sensitivity Calculator

-	Noema	Pico Veleta	Yebes	Onsala	Metsähovi	VLBA	GBT	KVN	LMT	ALMA37
Effelsberg	32	64	78	128	304	150-290	29	136	56	21
Noema	-	26	32	52	124	60-120	12	56	23	8
Pico Veleta	-	-	63	104	246	120-230	23	110	46	17
Yebes	-	-	-	127	303	150-289	29	136	56	21
Onsala	-	-	-	-	496	245-470	47	222	92	34
Metsähovi	-	-	-	-	-	580-1120	111	527	218	80
VLBA	-	-	-	-	-	287-1047	55-106	259-503	107-208	39-76
GBT	-	-	-	-	-	-	-	50	21	8
KVN	-	-	-	-	-	-	-	-	98	36
LMT	-	-	-	-	-	-	-	-	-	15

Baseline Sensitivity:	to Effelsberg: 20-300 mJy
	to Noema: 8-125 mJy
	to GBT: 8-111 mJy
	to ALMA: 8-80 mJy

Array Sensitivity (1 sigma):	0.087 mJy/hr (Europe+VLBA)
	0.052 mJy/hr (Europe+VLBA+GBT)
	0.029 mJy/hr (Europe+VLBA+GBT+ALMA)

	These numbers have to be increased by a factor of exp(tau*A) , i.e. for tau=0.1 and airmass A= 1/sin (elv) = 2, the factor is 1.22
	Depending on weather, the phase stability and atmospheric coherence time can vary between 10-180 seconds.
	Important Note: Because of antenna pointing, calibration and phasing of ALMA/NOEMA the typical VLBI duty cycle is 0.5. This means that for 1 hour of on source VLBI time, 2 hours of real observing are required.

Assuming the following observing parameters:

Mode:	MK6, 4096-16-2 (DDC), single polarisation
Bandwidth:	512 MHz per polarisation
Integration time:	10.0 sec (typical coherence time)
Threshold:	7.*sigma
Sampling:	2 Bit


Useful formulae:

B. Simulated uv-coverage for the Global 3mm-VLBI Array


Below we show 3 types of uv-coverages for sources with different declinations. In these simulations we assumed 12 hrs of observing time, 50% duty cyle, and a VLBI array consisting of 5 European and 8 VLBA antennas. ALMA, the LMT and the KVN are not yet included in the simulation. 1. for a source at dec=70 (click here) 2. for a source at dec=40 (click here) 3. for a source at dec= 0 (click here)

1. uv-plot of a source with a declination of 70 degree

2. uv-plot of a source with a declination of 40 degree

3. uv-plot of a source with a declination of 0 degree