IAA SETI Committee
Subcommittee on Post-Detection Science and Technology
Room C5, Riocentro, Rio de Janeiro, Brazil
October 4, 2000



  • Ray Norris (chair)
  • Doug Vakoch
  • Robert DeBiase
  • Donald E. Tarter
  • Dan Werthimer
  • Seth Shostak
  • Carol Oliver
  • H. Paul Shuch
  • Bela Balars
  • Mike Davis
  • Jack Welch
  • Tom Pierson
  • Jill Tarter
  • Guillermo A. Lemarchand

1. Welcome
2. Summary of activities of SETI PDC


2.1) web sites

  • public web site on www.atnf.csiro.au/~rnorris/SETI
  • password-protected private web site on www.atnf.csiro.au/~rnorris/SETI/pdc
  • note that it would be desirable to move the private website to a higher-capacity server with tighter security


2.2) Informal meeting of the SETI PDC at the IAU GA

3. Membership

At the IAU meeting, and in subsequent email discussion, it was agreed to invite:

  • Paul Horowitz
  • Dan Werthimer
  • Paul Shuch
  • Doug Vakoch
  • Ben Finney

Dan Werthimer, Paul Shuch, and Doug Vakoch have been invited and have agreed to join the group. Paul Horowitz and Ben Finney had not yet been contacted but will be contacted shortly.

It would also be useful to have members representing major observatories (e.g. NRAO, MPIfR) and members who are expert in the following fields:

  • RFI analysis
  • Cryptography
  • Information science
  • Media
  • Law

Nominations for experts in these fields would be welcome. It was also discussed whether it would be useful to have some representation from the security or military agencies. At this stage, it was felt best to use existing informal links into these agencies.

It was also suggested that it would be useful to ask each member of the PDC to post a short biography.

4 How to make the SETI PDC credible and effective?

Suggestions included:

  • Get involved at an early stage - don't wait until a putative detection is cast-iron, by which time other groups will have seized the initiative.
  • Ensure we have full communication within the group at an early stage - this would have prevented wasted effort in the EQ Peg hoax.
  • We need to set up an emergency drill or action plan to that all members of the group know what to do in the event of a putative detection


5 The Rio Scale

Jill Tarter gave a presentation of a paper by Ivan Almar and herself on the proposed "Rio scale" for ranking the significance of a putative SETI detection. This triggered a significant discussion. There was an enthusiastic consensus that an approach along these lines was an excellent idea, but significant debate about how exactly the various factors should be ranked. Suggestions included the following:

  • The ranking should be based on objectively measurable observables (e.g. characteristics of the signal or status of the observer) rather than inferred quantities (e.g. distance to the transmitter).
  • Different factors need to be combined with different weights
  • Flux density should be a factor
  • Who should make the rankings? Averaging assessments from several people makes it more believable than the opinion of one individual.
  • The final number should be in the range 1-10 (or 0 to 10) which is what people are used to, rather than 1-15
  • Important to respond quickly - thus we need a 24-hour PDC
  • We need to keep open the possibility of having multiple axes on the graph
  • The degree of consensus between the rankers should give an indicator of credibility of the answer
  • Some axes should be ranked only by experts in that field
  • For all axes, it will be important to have a median score which means "don't know"
  • Use logarithmic rather than linear scales
  • Should we separate "credibility of a detection" from other factors? What does "significance" mean?
  • On the other hand, important to come up with one number for simplicity.
  • Should we look at previous putative detections? It would be interesting to retrospectively assign numbers to the EQ Peg hoax, the "Wow" signal, the "Contact" detection, etc, as a guide and calibration to what these numbers mean.
  • How often do we want to get involved in doing this?
  • Need a log scale for believability of a detection (e.g. 10-6 to 1). I.e. just assign a probability
  • Maybe best to multiply by the probability and then take a log (NB this is the same as adding a number!)
  • Is 24 hours too short a response time? Is it too long?
  • If we have hard info, we should go public asap. Otherwise leave till a maximum of 24h before responding publicly.
  • Keep it integer for simplicity
  • There was some scepticism of our ability to produce a quantitative ranking with any authority or credibility.
  • We should err on the side of caution so as not to undermine the credibility of this group
  • We need to get some formal recognition of this "Rio scale". After we have all agreed on the details, we should attempt to get formal recognition by the IAA/IAU/whatever. Should we make an IAA press release? Perhaps a joint press release with a press organisation?

Other factors that it was felt was significant included:

  • Who made the detection - was it a known SETI group/astronomer/etc.?
  • Were there repeat observations?
  • Was there independent confirmation?
  • Was there any evidence of hacking or other indicators of antisocial behaviour?
  • What was the manner of the announcement - did they follow the protocol or go directly to the press?
  • What is the signal/noise ratio?
  • Is it a repeatable or transient detection?
  • Is the detection accompanied unreasonable claims such as "certainty"

There was a consensus that the PDC needed to have an "action plan" setting out the steps for response at short notice. Seth Shostak and Carol Oliver also pointed out that they had proposed such an action plan some while ago.



  • RPN to consult with Jill Tarter and Ivan Almar how to develop the Rio scale.
  • RPN to invite Paul Horowitz and Ben Finney to join the PDC
  • RPN to compile list of observatory contacts
  • All to nominate new members in relevant fields/institutions
  • All to submit a short bio for inclusion on private web page
  • RPN to pursue further issues:
  • Secure/high bandwidth web server + mirror
  • Start discussion on action plan