Minutes of the Archeops meeting
CRTBT Grenoble 6-7 May 1999
from FXD (uncomplete) notes

B. Hebral: Welcome

A. Benoit: Introduction

K. Madet: Vacuum tests in Toulouse (without insulation)

K. Madet: Bolometer platform, temperature regulations

A. Benoit: Electronic, readout, telemetry
- Mac in Palma de Mayorca needed
- How long do we keep contact?
- FET noise
- 18 channels (4 for the screens), 14 available so far: 7 thermometers
(4 regul, 3 focal plane), 6 bolometers
- TM rate: 108 kbits/sec
- only compressed data (for both bolometer and stellar sensor): To Be tested on real and simulated data
- TC rate: 18 bits every 10 seconds (very slow) Higher rate just
before launch
- commands are sent back into journal blocks TM

L. Guglielmi: On-board recorder
- small problem with DRAM which is needed for the operating system
(unsafe with cosmic rays)
- ready at the end of May
- 300mW consumption
- to be tested with the on-board transputer

B. Maffei: Bolometers and cold optics
- Expected performance for 1999 Archops flight
143 217 GHz
160 350 pW/K
0.5 0.5 10^-12 J/K
2 1 millisec
1.2 1.9 10^-17 W/Hz1/2 Johnson and phonon noise only
- First tests yield different values between CRTBT and QMW
measurements: to be redone

- Cold optics: 5 pixels are made : 3 at 143 GHz, 2 at 217 GHz,
possibility of a smooth horn pixel (for high frequency pixel),
following discussion about need for high frequency monitor as in
- 6 bolometers are available.
- Transmissions were measured for the back-to-back horns and the
filters, at 10K, 2K, 0.1K
- The 1.6 K filter stage: low-pass for 143 and bandpass for 217
- Gunn diode test of the optics at 180 GHz: at 22 deg. down to 27 dB

J. Ch. Vanel: Calibration cryostat
- ready and tested: 6 to 30K
- provides a global sensitivity test of the cryostat and bolometers
- measure time response: frequency measurements may yield a different
answer from pulse measurements with a chopper. Chopper can also be
used for rough bandpass checks
- to be tested with archeops cryostat

D. Santos: Optical characterisation
- beam determination
- use a modulated 8 Hz source made with sectors in a disk of 110cm
diameter with DeltaT of 50K (regulated with 1%) and a mask
- show diabolo data at POM2 on this modulated source
- Neron run shoud characterise the geometry and main beam
- pointing platform is ready (and was visited)

S. Hanany: The telescope
- Design (1.5m projected diameter 0.8 for the secondary)
- Baffling has to be discussed, models are necessary
- Use Gunn diode to measure possible leaks and straylight around the
gondola at Trapani
- Mirrors are at CRTBT (and were visited): surface roughness is better
than lambda/100, overall figure is lambda/20 (lambda>1 mm)
- 45 and 10 kg for the primary and secondary mirrors
- overall homology with the gondola so the overall shape does not
change with thermal contraction during flight.

S. Hanany: Goals of the Trapani Test Flight
- inflight detector noise, loading, responsivity
- cryogenic performance: 0.1K for 24hours
- Telescope and horn optical performance: main and side lobes
- Scan strategy: stability and pointing reconstruction accuracy,
pendulations,atmospheric noise, relative accuracy
- Signal compression and reconstruction
- Quick-look analysis (e.g. Fourier Transform on many time scales)
- Atmospheric contribution
- use galaxy as the poor man's pointing reconstruction (JLP)
- use sunset and sunrise (and Moon?) to measure sidelobes

A. Benoit: Data acquisition
- description of archeops.h and its different versions
and blocks (typically 2.5 bolometer blocks
per second)
- block types include
parameters (fixed)
reglage (variable)
stellar sensor
compressed bolos (1.5 kbyte)
compressed stellar sensor (2.2 kbyte)
gyros (0.3 kbyte)
and so on
- ground-segment configuration (mac + pc-linux + peripherals)
- due to low TC, set up automatic procedures
- safety modes (valve,...)

R. Gispert: Off line processing
- Global approach for Planck: archeops will gradually tests this
- raw data: TM blocks in binary files of about 5 minutes of data
- TOI: (time ordered information)
{time, info1, info2, ...} replicated
Need to develop basic tools TBD to save and retrieve required TOI
- maps : full sky, and subsets (different pixelisation and projection
schemes are needed)
- Heterogeneous data coming from ground-based studies and the
instrument and telescope description and models.
- Existing toy model: TangoJ "observed map simulator" developped in
pure Java.
- computers at Trapani

7 May

F.X.Desert: expected sensitivity
- Beam is 7.2 arcmin.
- Trapani : S. Hanany raises the question of the beam
sampling: Trapani will give 4.5 arcmin per sample, if one turns with
2.64 rpm, i.e. 12 degrees per second.
For each beam and each bolometer, 51 milliseconds are spent. There are
426 000 beams on the covered sky, each will be measured with 1sigma=
145 and 122 (10^-6 in DeltaT/T) for 143 and 217 GHz respectively.
For each sky pixel of 20 arcmin square, a total integration time of
780 millisecond will have been spent per channel, 55 200 pixels will have been
visited in 6 dark hours (15% of sky), each will be measured with
1sigma= 37 and 31
- Kiruna : these last figures are now 12 and 10, 25% of the sky are covered
in 24 hours.
- Background is expected to be 1, 2, and 8 picoWatts, photon noise is
1, 2, ..., detector noise is <2, 3 ( in 10^-17 W/sqrt(Hz)) at 143, 217
and 353 GHz.

F. Bouchet: Expected scientific output from Trapani flight
- actual sky expectation
- tools to predict timelines

J. Delabrouille: Simulation software
- discussion about colours and subtraction techniques
for all expected systematic effects
- IDL routines to compute effects of sidelobes as applied to the Earth
surface with various temperatures.

P. De Bernardis: Gondola and pivot
Gondola: design done, inner frame is at CRTBT (visited today), outer
frame (end of May). Size is 2700 by 2000 by 3600 (height).
Pivot modified to hold 1 ton.= (500 kg for payload, 250 for ballast,
100 for floatation device, 110 TC-TM, + misc.)
Sensor platform: Gyros, Tilt-meter, micrometric trim
Baffling: recognised as a key issue (problem with wind shear,

S. Masi: Star sensor
1 arcmin resolution in elevation, 1.9 degree covered in elevation
2 lines of 46 photodiodes each are multiplexed (one line is shown at CRTBT
during the meeting) (size is 4 by 1 mm). Glass mirror. integration
tests to be done.

J. Bartlett: Redundancy
- The final product is a measure of the CMB "noise". the only way to
evaluate and subtract "instrument" noise is to have redundancy.
- The redundancy is recognised as critically low for Trapani (except
near the North Pole). Kiruna
will offer a much better redundancy at various time scales.

A. Benoit and P. De Bernardis: Trapani July 1999 Flight campaign
- Launch window: July 8-17, 1999 new moon
Trapani starts on June 15, mounting, assembling, software testing,
TC-TM testing, test far sidelobes, RF sensitivity, role of space
agency antenna, baffling, end-to-end test on July 1st.
- Palma team: to be defined
- Spain recovery team
- Before Trapani campaign:
week 1, May 10-12 : R(T), IV, Alignment, star sensor
week 2, May 17-21 : calibration cryostat, test of platform
week 3, May 25-28 : Neron, on-board recorder, test pivot in Italy,
star sensor
week 4, May 31-Jun 4 : optical efficiency, spectral bands
week 5, Jun 7-11 : HF channel
week 6, Jun 14-18 : transportation.

List of participants

Eric Aubourg  CEA eric.aubourg@cea.fr
Jim Bartlett  OMP bartlett@astr.obs-mip.fr
Alain Benoit  CNRS/CRTBT benoit@labs.polycnrs-gre.fr
Yvan Blanc CNES yvan.blanc@cnes.fr
Francois Bouchet     IAP bouchet@iap.fr
Philippe Camus CSNSM camus@csnsm.in2p3.fr
Nuno Castanheira CNRS/CESR nuno.castanheira@cesr.fr
Paolo De Bernardis Univ Rome paolo.debernardis@roma1.infn.it
Jacques Delabrouille PCC-CdF j.delabrouille@cdf.in2p3.fr
F.-Xavier Desert LAOG desert@obs.ujf-grenoble.fr
Philippe Filliatre ISN filliatr@isnhp8.in2p3.fr
Bernard Fouilleux LAOG fouilleux@obs.ujf-grenoble.fr
Fred Gannaway QMW f.gannaway@qmw.ac.uk
Bertrand Gautier CNRS/CRTBT gautierb@labs.polycnrs-gre.fr
Yannick Giraud-Heraud PCC-CdF ygh@cdf.in2p3.fr
Richard Gispert IAS gispert@ias.fr
Laurent Guglielmi PCC-CdF guglielmi@cdf.in2p3.fr
Jacques Ha"issinski LAL jhaiss@lal.in2p3.fr
Shaul Hanany Univ. Minnesota hanany@physics.umn.edu
Jean Kaplan PCC-CdF kaplan@cdf.in2p3.fr
Karin Madet CNRS/CRTBT madet@polycnrs-gre.fr
Bruno Maffei QMW b.maffei@qmw.ac.uk
Philippe Marty IAS marty@ias.fr
Silvia Masi Univ Rome silvia.masi@roma1.infn.it
Fabrice Naraghi ISN naraghi@isn.in2p3.fr
Guy Perrin ISN gperrin@isnhp1.in2p3.fr
Jean-Loup Puget IAS puget@ias.fr
Henri Rodenas CNRS/CRTBT rodenas@polycnrs-gre.fr
Daniel Santos ISN santos@isn.in2p3.fr
Jean-Claude Vallier CNRS/CRTBT vallier@polycnrs-gre.fr
Jean-Charles Vanel PCC-Cdf vanel@cdf.in2p3.fr
Didier Vibert IAP vibert@iap.fr
Yves Zolnikowski LAPP zolnikowski@lapp.in2p3.fr