1. Our “Contact” scenario. ETI at the VLA.
The aim is to discuss the feasibility of an ETI signal detection
using the VLA with reasonable assumptions.
Justification for this project is VERY subjective, so we are
going to skip over to the technical specs.
ERIS 2011, Rimini, IT

2. Emmiter: Narrow – band, beamed, 100 m antenna, 1 MW transmitter power.
5 kpc distance – general direction towards center of Galaxy.
L/D = 0.21/100=0.0021
tg(a/2)=(d/2)/r -> d=2*r*tg(a/2)=5.37*10^12 [km]
BW_ETI_eff = 10*20 kHz channels = 200 kHz
BW_ETI= 10 MHz
Hops inside 10 MHz band –> message content is (P)FSK encoded
(in the beacon stage).
F_Earth = 1*10^6 / (9*10^31 * 200 * 10^3) = 5 [uJy]
dL/L=v/c – compensate for planetary motions,
assume ETI emits at HI freq in our rest frame to make the detection
easier for us.
df=v/L=30*10^3/0.21=143 kHz; 2*df = 286 kHz
ERIS 2011, Rimini, IT

3. VLA Observe at night ! - Sun hindrance in L band.
VLA in A array config; 36 km across
16 MHz sub-band bandwidth
2 pol. Products
62.5 kHz channel width – sample their band with 3 channels.
Make an image cube, to distinguish the “source” from RFI
Same position on sky, different “velocity”
Real RFI decorelates on large baselines
RMS noise of this config – 1 hour “stare” (VLA exposure calculator) is:
70 uJy / beam (summer sky assumed, Sagittarius visible).
RMS brightness temperature: 14 K
VLA synthesized beam size: L / B = 0.21 / 36*10^3 = 6 urad.
ERIS 2011, Rimini, IT

4. 6 urad = 1.2 “
Pixel size (shannon) = 1.2 / 4 = 0.3”
Beam area = 2^2 * 3.14 = pix / beam
So, RMS noise is: 70 uJy / beam / pix / beam = 5.5 uJy
S / N = 5 / 5.5 ~ 1
The “Sanaz” calibration method can easily bring out this “source”
From the noise !
So, this setup is entirely possible.
ERIS 2011, Rimini, IT

5. alien Aleksandar Shulevski Darko Donevski Katinka Gereb Sanaz Kazemi
Again, VLA???
alien
Aleksandar Shulevski
Darko Donevski
Katinka Gereb
Sanaz Kazemi
Omar Roldan
Juan Palacios Fonseca
ERIS 2011, Rimini, IT