Issue |
Astron. Astrophys. Suppl. Ser.
Volume 121, Number 2, February 1997
|
|
---|---|---|
Page(s) | 393 - 404 | |
DOI | https://doi.org/10.1051/aas:1997322 | |
Published online | 15 February 1997 |
Sub-degree CMB anisotropy from space
II. In-flight calibration
1
Istituto di Fisica Cosmica, CNR, Milano, Italy
2
Dipartimento di Fisica, Universita' di Tor Vergata, Roma, Italy
3
Istituto TESRE, CNR, Bologna, Italy
Send offprint request to: M. Bersanelli
Received:
7
March
1996
Accepted:
7
June
1996
In the context of the COBRAS/SAMBA
mission study1, we discuss in-flight
calibration of extended sky maps of the microwave
sky using celestial sources. We simulate the
observations in order to assess the accuracy
obtainable for absolute and relative calibration
of the Low Frequency Instrument (LFI), operating
in the 30-130 GHz range. Accurate calibration
can be achieved using the CMB dipole signal,
. With conservative assumptions
on the effect of Galactic contamination, we find
that the CMB dipole will provide absolute
calibration accuracy
(limited by the
COBE-DMR uncertainty on
) on
time-scales of about 10 days at all frequencies and
for the entire mission lifetime. Long-term
calibration with accuracy
can be obtained
using the spacecraft orbital velocity. Additional,
independent calibration will be provided by the
observation of external planets. We also describe
the capability of the proposed scanning technique
to detect and remove long-term
instrumental drifts, and show that these effects, if present,
can be controlled and removed with an
overall negligible impact on the data uncertainty.
Key words: cosmic microwave background / radio continuum: general / space vehicles
© European Southern Observatory (ESO), 1997