<title>OSETI: interstellar laser communications link (iLCL): parameters, mechanisms, concepts</title>

Abstract

Can optical SETI contact, and possibly communication, be established via Electro-Optic means, with ETI 'technical civilizations', who like us, potentially might be residing with the galaxy? Specifically, can laser 'Beacons' or interstellar Laser Communications Links (iLCL), be implemented with current or future, but foreseeable Electro-Optic Technology (EOT)? If so, what are the parameters, mechanisms, and concepts by which such systems could be mechanized? If indeed, electro-optic UV/VIS/IR sensors would detect such signals from a remote extraterrestrial origin, from where, and from how far away, might such signals come from? How would we respond to them? The theme, here envisioned, is that a 'Listen-only' strategy could/should be complemented with EOT/laser transmissions by us, terrestrials, so-as to result in a 'receive and transmit' strategy. This form of proactivity could markedly enhance the probability of ultimate successful contact. It is projected, that this can be accomplished by the use of suitably configured, space-based High- Power Laser Sources. Such devices would probably be operating at short optical wavelengths (VIS and UV), into diffraction limited large aperture optics, pointed with high precision and accuracy, at candidate stellar systems. A SNR link-analysis was carried out, for such iLCL systems, in both a pulsed and CW- mode of operation. Laser systems were analyzed whereby a one Mega Watt average output power assumption, was utilized as a baseline. Operating ranges, pulse energies, and pulsewidths were parametrized over a spectrum of optical wavelengths. It is shown that UV/VIS/IR pulsed laser systems operating in the 'Beacon' or lower data-rate mode, might variously operate over such interstellar ranges, 10-3,000 light years at imputed 'optimistic'- and 'nominal'-regimes of likelihood of contact. It is recognized that 'pessimistic'-regime ranges of 3,000-10,000 light years or more, might be required to surmount the Drake Equation probabilities to establish communicative contact. For contact to be made a transmit-receive SYNCHRONISM, accounting for propagation delay time, must exist to enable a 'look' when a signal is present at the reception point. Additionally, a sufficient COEVALITY must exist, to prevent an evolutionary time-phase-delay between communicating agencies, from establishing and maintaining an enduring oSETI-type iLCL contact.