The release by the NSA of thousands of declassified UFO documents has the blogosphere and twitter-sphere ablaze and speculations running rampant that somewhere in those files is the 'smoking gun' for alien craft in the skies of our planet. The website for accessing the documents can be found here:
But don't hold your breath trying to turn up evidence for extraterrestrials. There won't be any. Or, let me correct that by noting there might be some semblance of signal - but it's buried in tons of noise. Do you have the patience to sift through it all? When the JFK Records Act saw millions of files released from back in 1992, only a relatively few determined and hardy researchers had the diligence to plumb through them to turn up assorted nuggets, such as Oswald's CIA files - showing he'd at least been a contract agent for the 'company'. Further work by stalwarts such as Peter Dale Scott also identified the key telegrams from the CIA Mexico City station showing indisputably how Oswald had been framed to take the fall. Of course, it's ironic that scads of lazy critics - who like to shoot from the hip on the whole JFK assassination conspiracy issue - couldn't bestir themselves to lift one pinky finger to find a single file themselves.
Expect the same reaction from the lazy dopes if you happen to hit pay dirt by going through the UFO files from the link above. "The truth is out there" - yes, but few in the government want you to see it, as in the Kennedy assassination conspiracy.
Does this mean we are talking about actual alien ships? No, not necessarily. A common misperception is that UFOs are “flying saucers” or space ships. However, this is actually only one possible hypothesis among several. This is evident in the late J. Allen Hynek's exacting UFO definition
“A UFO is the reported perception of an object or light seen in the sky, the appearance, trajectory and general dynamic behavior of which do not suggest a logical, conventional explanation and which is not only mystifying to the original percipients but remains unidentified, after close scrutiny of all available evidence by persons who are technically capable of making a common sense identification, if one were possible.”
The gist of the definition - however lengthy = is that one must not automatically jump to any conclusion that conflates the UFO with an extraterrestrial craft. The difficulty in formulating UFO hypotheses, and interpreting UFO reports, is a first-hand experience for me. Not only have I investigated other people's reports (inevitable if one is involved in astronomy) and published the results but I've observed a "UFO" myself. The incident occurred in March of 1962 at the opening of a shopping center in Carol City, Florida. While awaiting the start of festivities I happened to look up at the night sky, being the amateur astronomer that I was. Amazingly, I witnessed a brilliant orange disc, at least the same diameter as a full Moon, moving rapidly from north to south.
It hovered for two to three seconds above the crowd and I detected the odd "Oooh" or "Aaah" from random spectators. Thus, I knew I was not having a simple hallucination (at least not by myself!) The most ironic and notable thing to me was the complete absence of sound. No whirring, like one would expect from a helicopter's propeller blades, or engine noise. The object - if "object" it was - appeared to be a light source rather than just reflecting light from elsewhere. After about three seconds it took off due south at what I estimated to be an incredible speed. As a seasoned sky observer, even at the age of 16, I was able to quickly eliminate all known man-made or natural objects from consideration. The exceptional luminous and dynamical behavior allowed this. Nevertheless, to this day I am not prepared to pinpoint a specific hypothesis in any dogmatic sense. Nor am I prepared to assert it as a "craft" from another planet.
But let's say one is looking for some kind of signal from the NSA files that a real artifact exists, what would one look for? What sort of parameters, physical aspects?
As a good preliminary test, one can do no better than enlisting Physicist Edward U. Condon’s Air Force- commissioned Scientific Study of Unidentified Flying Objects (1969, NY Times Books) While most of the cases are exposed as either natural or meteorological phenomena – or possible hoaxes- one case stands out: Case 46, p. 396 from McMinnville Ore. (11 May, 1950) that concludes - and I quote, from p. 407
:"This is one of the few UFO reports in which all factors investigated: geometric, psychological and physical appear to be consistent with the assertion that an extraordinary flying object- silvery, metallic and disc shaped flew within sight of two witnesses. "
I found the best part of the case study was the photometric analysis (pp. 402-06). This was essential in order to discriminate luminance conditions between a hypothetical hand model nearby and an actual, extraordinary, distant flying object. The key observation made by the investigators was:
"The shadowed bottom of the UFO (see image) has a particularly pale look suggestive of scattering between observer and object. If such scattering is detectable it may be possible to make some estimate of the distance involved".
From there they list a sequence of possible interpretations, including: optical fabrication or double exposure (rejected because the UFO is darker than the sky background luminance); a retouch of a drawn image (rejected because analysis of the negatives disclosed they were unretouched); physical fabrication using a 'frisbee' hand spun model (rejected because the UFO displays an off-axis pole which is never seen displaced, i.e. in rotation); model suspended from a wire (similar positions in each photo -so possible), and extraordinary flying object (since photometry suggests a large distance).
So, in the end, the last two interpretations had to be analyzed for consistency with the least likely of the two rejected.
The investigators proceeded by computation of the luminance, or the apparent brightness of an object at a distance r, normalized relative to some intrinsic value B(o) at r(o), viz p. 402:
B = B(sky) (1 - exp(-br)) + B(o) exp(-br)
where b is the scattering coefficient. In the equation, the first term (with B(sky)) represents scattered light and the second term, extinction. As the investigators noted (ibid.):
"Since all measures must be based on the witnesses' two photographs, we will determine b for the given day from the photographs themselves. Normalizing all brightnesses (measured from the film and assuming that the images fall on the linear portion of the gamma curve (see- e.g. http://en.wikipedia.org/wiki/Gamma_correction) to that of the sky near the horizon, i.e. on a line within a few thousand feet of the ground, where the UFO is constrained to be by the reported cloud height and probable nearness to the camera, we have:
B = 1 + exp(-br)[B(o) - 1]"
From the above, if the object is sufficiently distant one would have:
exp(-br) -> 0
B = 1 + exp (0)[B(o) - 1] = 1 + [B(o) - 1]
and B equals the sky brightness. (in optical terms, the optical depth t >> 1)
To ascertain whether the claimed sighting photographed is a fake then, all that's needed is to solve for the distance r, given a zero distance luminance B(o) cmopared to an observed luminance B. As can be seen from the equation, to do this one needs to obtain the scattering coefficient, b.
The investigators used densitometric analysis to obtain an assorted range of values for the luminance B, for different objects appearing in the photographic image - these are presented in Table 2, from the Case Study. (Shown, with comparison of two plates, 23 and 24). Since the investigators knew the distance of 'Hill 2' at 2.2 km then photometry indicated B = 0.685 for the distance hill, while the foreground foliage yielded B = 0.403.
Processing all this data in concert, the investigators obtained the distance r = 0.32 km, or just over 1,050 feet as the distance to the object - nearly one fifth of a mile. The investigators graphically illustrated the domains of the two hypotheses via their graph (Fig. 3) which is appended here. As they note (p. 406):
"If the object is a model suspended from a wire only a few meters away the surface is some 37% brighter (B = 1.21 v. B = 0.885) than the tank and the shaded portion is probably more than 40% brighter than the shadow on the tank...nearly impossible to maintain in the face of the photometry.
The shadowed side of the UFO appears so bright that it suggests significant scattering between it and the observer"
In other words, conforming with the distance calculated from the luminances..
The investigators graphically illustrated the domains of the two hypotheses via their graph shown below:
The point of all this is there appears to be at least quantitative -photometric evidence for the existence of extraordinary craft if one knows how (and where) to look for it.
The $64 dollar question is: Are most interested people qualified to be able to perceive the evidence even if it's staring them in the face?
I suspect that depends on one's scientific background, or at least exposure to basic physics principles. This includes those pertaining to luminance and relation to brightness, as well as geometrical factors such as being able to derive linear scales from angular - e.g. as observed against the sky background.
So, by all means have a look at the released UFO files, but always be aware of what it is you are seeing, and also whether the parameters, physical aspects are sufficient to make any kind of determination. And lastly, whether you are really qualified to make any determination.
 Transient Optical Phenomena of the Atmosphere - A Case Study, in The Journal of the Royal Astronomical Society of Canada, Vol. 74, No. 3, June 1980.