Publication Date:
2014
abstract:
We discuss the methods employed to photometrically calibrate the data
acquired by the Low Frequency Instrument on Planck. Our calibration is
based on a combination of the orbital dipole plus the solar dipole,
caused respectively by the motion of the Planck spacecraft with respect
to the Sun and by motion of the solar system with respect to the cosmic
microwave background (CMB) rest frame. The latter provides a signal of a
few mK with the same spectrum as the CMB anisotropies and is visible
throughout the mission. In this data releasewe rely on the
characterization of the solar dipole as measured by WMAP. We also
present preliminary results (at 44 GHz only) on the study of the Orbital
Dipole, which agree with the WMAP value of the solar system speed within
our uncertainties. We compute the calibration constant for each
radiometer roughly once per hour, in order to keep track of changes in
the detectors' gain. Since non-idealities in the optical response of the
beams proved to be important, we implemented a fast convolution
algorithm which considers the full beam response in estimating the
signal generated by the dipole. Moreover, in order to further reduce the
impact of residual systematics due to sidelobes, we estimated time
variations in the calibration constant of the 30 GHz radiometers (the
ones with the largest sidelobes) using the signal of an internal
reference load at 4 K instead of the CMB dipole. We have estimated the
accuracy of the LFI calibration following two strategies: (1) we have
run a set of simulations to assess the impact of statistical errors and
systematic effects in the instrument and in the calibration procedure;
and (2) we have performed a number of internal consistency checks on the
data and on the brightness temperature of Jupiter. Errors in the
calibration of this Planck/LFI data release are expected to be about
0.6% at 44 and 70 GHz, and 0.8% at 30 GHz. Both these preliminary
results at low and high l are consistent with WMAP results within
uncertainties and comparison of power spectra indicates good consistency
in the absolute calibration with HFI (0.3%) and a 1.4sigma discrepancy
with WMAP (0.9%).
acquired by the Low Frequency Instrument on Planck. Our calibration is
based on a combination of the orbital dipole plus the solar dipole,
caused respectively by the motion of the Planck spacecraft with respect
to the Sun and by motion of the solar system with respect to the cosmic
microwave background (CMB) rest frame. The latter provides a signal of a
few mK with the same spectrum as the CMB anisotropies and is visible
throughout the mission. In this data releasewe rely on the
characterization of the solar dipole as measured by WMAP. We also
present preliminary results (at 44 GHz only) on the study of the Orbital
Dipole, which agree with the WMAP value of the solar system speed within
our uncertainties. We compute the calibration constant for each
radiometer roughly once per hour, in order to keep track of changes in
the detectors' gain. Since non-idealities in the optical response of the
beams proved to be important, we implemented a fast convolution
algorithm which considers the full beam response in estimating the
signal generated by the dipole. Moreover, in order to further reduce the
impact of residual systematics due to sidelobes, we estimated time
variations in the calibration constant of the 30 GHz radiometers (the
ones with the largest sidelobes) using the signal of an internal
reference load at 4 K instead of the CMB dipole. We have estimated the
accuracy of the LFI calibration following two strategies: (1) we have
run a set of simulations to assess the impact of statistical errors and
systematic effects in the instrument and in the calibration procedure;
and (2) we have performed a number of internal consistency checks on the
data and on the brightness temperature of Jupiter. Errors in the
calibration of this Planck/LFI data release are expected to be about
0.6% at 44 and 70 GHz, and 0.8% at 30 GHz. Both these preliminary
results at low and high l are consistent with WMAP results within
uncertainties and comparison of power spectra indicates good consistency
in the absolute calibration with HFI (0.3%) and a 1.4sigma discrepancy
with WMAP (0.9%).
Iris type:
1.1 Articolo in rivista
Keywords:
cosmic background radiation; instrumentation: polarimeters; methods: data analysis
List of contributors:
P., Collaboration; N., Aghanim; C., Armitage Caplan; M., Arnaud; M., Ashdown; F., Atrio Barandela; J., Aumont; C., Baccigalupi; A. J., Banday; R. B., Barreiro; E., Battaner; K., Benabed; A., Beno�t; A., Benoit L�vy; J., Bernard; M., Bersanelli; P., Bielewicz; J., Bobin; J. J., Bock; A., Bonaldi; L., Bonavera; J. R., Bond; J., Borrill; F. R., Bouchet; M., Bridges; M., Bucher; C., Burigana; R. C., Butler; B., Cappellini; J., Cardoso; A., Catalano; A., Chamballu; X., Chen; L., Chiang; P. R., Christensen; S., Church; S., Colombi; L. P., L.; B. P., Crill; A., Curto; F., Cuttaia; L., Danese; R. D., Davies; R. J., Davis; P. d., Bernardis; A. d., Rosa; G. d., Zotti; J., Delabrouille; C., Dickinson; J. M., Diego; H., Dole; S., Donzelli; O., Dor�; M., Douspis; X., Dupac; G., Efstathiou; T. A., En�lin; H. K., Eriksen; F., Finelli; O., Forni; M., Frailis; E., Franceschi; T. C., Gaier; S., Galeotta; K., Ganga; M., Giard; G., Giardino; Y., Giraud H�raud; E., Gjerl�w; J., Gonz�lez Nuevo; K. M., G�rski; S., Gratton; A., Gregorio; A., Gruppuso; F. K., Hansen; D., Hanson; D., Harrison; S., Henrot Versill�; C., Hern�ndez Monteagudo; D., Herranz; S. R., Hildebrandt; E., Hivon; M., Hobson; W. A., Holmes; A., Hornstrup; W., Hovest; K. M., Huffenberger; A. H., Jaffe; T. R., Jaffe; J., Jewell; W. C., Jones; M., Juvela; P., Kangaslahti; E., Keih�nen; R., Keskitalo; T. S., Kisner; J., Knoche; L., Knox; M., Kunz; H., Kurki Suonio; G., Lagache; A., L�hteenm�ki; J., Lamarre; A., Lasenby; R. J., Laureijs; C. R., Lawrence; S., Leach; J. P., Leahy; R., Leonardi; J., Lesgourgues; M., Liguori; P. B., Lilje; M., Linden V�rnle; M., L�pez Caniego; P. M., Lubin; J. F., Mac�as P�rez; D., Maino; N., Mandolesi; M., Maris; D. J., Marshall; P. G., Martin; E., Mart�nez Gonz�lez; S., Masi; M., Massardi; S., Matarrese; F., Matthai; P., Mazzotta; P. R., Meinhold; A., Melchiorri; L., Mendes; A., Mennella; M., Migliaccio; S., Mitra; A., Moneti; L., Montier; G., Morgante; D., Mortlock; A., Moss; D., Munshi; P., Naselsky; P., Natoli; C. B., Netterfield; H. U., N�rgaard Nielsen; D., Novikov; I., Novikov; I. J., O'Dwyer; S., Osborne; F., Paci; L., Pagano; R., Paladini; D., Paoletti; B., Partridge; F., Pasian; G., Patanchon; D., Pearson; M., Peel; O., Perdereau; L., Perotto; F., Perrotta; E., Pierpaoli; D., Pietrobon; S., Plaszczynski; E., Pointecouteau; G., Polenta; N., Ponthieu; L., Popa; T., Poutanen; G. W., Pratt; G., Pr�zeau; S., Prunet; J., Puget; J. P., Rachen; R., Rebolo; M., Reinecke; M., Remazeilles; S., Ricciardi; T., Riller; G., Rocha; C., Rosset; M., Rossetti; G., Roudier; Mart�n, J. A. Rubi�o.; B., Rusholme; M., Sandri; D., Santos; D., Scott; M. D., Seiffert; E. P., S.; L. D., Spencer; J., Starck; V., Stolyarov; R., Stompor; F., Sureau; D., Sutton; A., Suur Uski; J., Sygnet; J. A., Tauber; D., Tavagnacco; Terenzi, Luca; L., Toffolatti; M., Tomasi; M., Tristram; M., Tucci; J., Tuovinen; M., T�rler; G., Umana; L., Valenziano; J., Valiviita; B. V., Tent; J., Varis; P., Vielva; F., Villa; N., Vittorio; L. A., Wade; B. D., Wandelt; R., Watson; A., Wilkinson; D., Yvon; A., Zacchei; A., Zonca
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