IAA SETI Permanent Committee: Rio Scale
(Iván Almár and Jill Tarter, in the 51st International Astronautical Congress,
29th Review Meeting on the Search for Extraterrestrial Intelligence,
in Rio de Janeiro, Brazil, in October, 2000)
is a scale for assessing putative contacts with extraterrestrial intelligent entities.
It was devised in analogy with several other such scales,
and the higher a putative contact scores, the greater is its importance.
Type of Phenomenon
Method of Discovery
Distance
Reliability
Scores
Quality
Score
Type
Method
Distance
(Total)
Overall
Score
Quality
Reliability
Total Score
ETI: The Rio Scale version 2
An updated version of the Rio scale was recently proposed:
Forgan, Wright, Tarter, Korpela, Siemion, Almár, and Piotelat 2018
Rio 2.0: revising the Rio scale for SETI detections | International Journal of Astrobiology | Cambridge Core
It follows the original one in having (quality)x(reliability),
but its quality scale is revised and its reliability scale is much expanded.
All the descriptive text is quotes from the article, but the HTML formatting is mine,
and I have restated the algorithms.
Quality of the signal and its contents
What is the estimated distance to the source of the signal?
What are the prospects for communication with the source of the signal?
Is the sender aware of humanity/its technology?
Reliability of the evidence
How real and amenable to study is the phenomenon?
Is there a significant uncertainty about whether the phenomenon occurred/occurs at all?
How amenable to study is the phenomenon?
Is the discoverer of the phenomenon the same person/group that predicted that such a phenomenon would indicate the pres- ence of alien intelligence?
How certain are we that the phenomenon is not instrumental?
Does the phenomenon look like a known instrumental or psychological effect?
What chances do the instrument builders/experts in the method/observers of the phenomenon give that the signal is not instrumental?
How certain are we that the phenomenon is not natural or anthropogenic?
Is there a good reason to think the phenomenon is a hoax?
How does a wide community of experts assess the probabilty that there are any known sources of natural or anthropogenic signal that could explain the phenomenon?