ONGOING DISCUSSION "sine ira et
studio...."
(Tacitus, Annales - Incipit; ~ 100-117A.C.)
on:
Radiometer
effect in space missions to test the equivalence principle (and related issues on the different
design of the 3 proposed projects: Microscope, STEP and GG
Jyly 2001: Issue N. 13 of Class. Quantum Grav.
is published, containing the proceedings of the Symposium on "Testing the Equivalence
Principle in Space" (Septemper 4-7 2000, Ross Priory, Glasgow, Scotland).
Relevant to this discussion are the papers: "The
Microscope space mission" (Touboul and Rodrigues, PDF file 319
KB); "STEP error model development" (Worden,
Mester and Torii, PDF file 114 KB); "Can the
equivalence principle be tested with freely orbiting masses?" (Blaser,
PDF file 158 KB). The Symposium covered the STEP and Microscope projects, but not
the GG project (the GG scientists were not informed of the Symposium).
October 2001: Concerns on the radiometer effect and the
configuration of the accelerometer in the Microscope space mission, are brought to the
attention of the Chairman of the Fundamental Physics Advisory Group (FPAG) of ESA by
A. Nobili (Letter as PDF file, 17 KB)
December 2001: Motivated by the paper published in July
on "The Microscope space mission"
(Touboul and Rodrigues, PDF file 319 KB), the GG scientists have re-examined the
radiometer effect for this mission. As a result, the manuscipt "Radiometer
effect in the Microscope space mission" is brought to the attention of the Director
of Science at ESA (text of e-mail
message). Director answers "I have asked for advice on the issues you
raise."
January 2002: A revised version of the manuscipt "Radiometer effect in the Microscope space mission"
is brought to the attention of Dr Pierre Touboul, Principal Investigator of the Microscope
project. Copy also to FPAG members and to the Director of Science at ESA (text of e-mail message; Manuscript as PDF file, 67 KB)
January 2002: Pierre Touboul, Principal Investigator of
the Microscope project, answers on "Radiometer effect in the Microscope
space mission" (letter to A. Nobili in html
format; As PDF file obtained from
scanned images, 1.4 MB), and on the concerns raised in October 2001 (letter to FPAG in html format; As PDF file obtained from scanned images, 1.1
MB)
January 2002: Anna Nobili answers Pierre Touboul
(copy also to FPAG members and to the Director of Science at ESA). Convergence on
the main issues may be achieved in a few iterations (Letter as PDF file, 115 KB).
April 2002: Albrecht Ruediger circulates the
manuscript: Residual gas effects in space-borne position
sensors . He points out the presence of "an even stronger noise source due
to the temperature dependence of the outgassing rate of the sensor cage" and
questions the way radiometer effect has been evaluated so far.
