Abstract
We have tracked the spectral responsivity of the ultraviolet channels of the UVCS (Ultraviolet Coronagraph Spectrometer) instrument on SOHO by repeated observations of a stable hot star. We demonstrate first that the ultraviolet spectral irradiance of the Be star ζ Tau (HD 37202) for the 100- to 125-nm wavelength range has been sufficiently constant for our purposes when measured periodically over the course of the SOHO mission. We then use ζ Tau as a radiometric transfer standard to determine an average decrease beginning in November of 1998 of 13.0% per year in the responsivity of the UVCS O vi channel for wavelengths near H i Ly α and for a particular UVCS unvignetted aperture used for science observations. The calibration tracking method involves separating two ζ Tau spectral regions that are overlapped on part of the detector. The change in the responsivity of UVCS/SOHO began in late 1998 as determined by comparison of simultaneous observations of the corona carried out with UVCS/SOHO and the freshly-calibrated UVCS instrument on the Spartan 201 satellite in early November of 1998.
Similar content being viewed by others
References
Boggess, A., Carr, F.A., Evans, D.C., Fischel, D., Freeman, H.R., Fuechsel, C.F., Klinglesmith, D.A., Krueger, V.L., Longanecker, G.W., Moore, J.V.: 1978, Nature 275, 372.
Cosmo, M.L., Smith, P.L., Atkins, N., Suleiman, R.M., Gardner, L.D., Kohl, J.L.: 1999, Proc. SPIE 3764, 161.
Fleck, B., Domingo, V., Poland, A.I.: 1995, Solar Phys. 162, 1.
Gardner, L.D., Kohl, J.L., Daigneau, P.S., Dennis, E.F., Fineschi, S., Michels, J., Nystrom, G.U., Panasyuk, A., Raymond, J.C., Reisenfeld, D.J., Smith, P.L., Strachan, L., Suleiman, R., Noci, G., Romoli, M., Ciaravella, A., Modigliani, A., Huber, M.C.E., Antonucci, E., Benna, C., Giordano, S., Tondello, G., Nicolosi, P., Naletto, G., Pernechele, C., Spadaro, D., Siegmund, O.H.W., Allegra, A., Carosso, P.A., Jhabvala, M.D.: 1996, Proc. SPIE 2831, 2219.
Gardner, L.D., Atkins, N., Fineschi, S., Smith, P.L., Kohl, J.L.: 2000, Proc. SPIE 4139, 362.
Gardner, L.D., Smith, P.L., Kohl, J.L., Atkins, N., Ciaravella, A., Miralles, M.P., Panasyuk, A., Raymond, J.C., Strachan, L., Suleiman, R.: 2002, In: Pauluhn, A., Huber, M.C.E., von Steiger, R. (eds.) The Radiometric Calibration of SOHO, ISSI Scientific Report SR-002, 161.
Guo, Y., Huang, L., Hao, J., Cao, H., Guo, Z., Guo, X.: 1995, Astron. Astrophys. Suppl. 112, 201.
Kohl, J.L., Gardner, L.D., Strachan, L., Hassler, D.M.: 1994, Space Sci. Rev. 70, 253.
Kohl, J.L., Esser, R., Gardner, L.D., Habbal, S., Daigneau, P.S., Dennis, E.F., Nystrom, G.U., Panasyuk, A., Raymond, J.C., Smith, P.L., Strachan, L., van Ballegooijen, A.A., Noci, G., Fineschi, S., Romoli, M., Ciaravella, A., Modigliani, A., Huber, M.C.E., Antonucci, E., Benna, C., Giordano, S., Tondello, G., Nicolosi, P., Naletto, G., Pernechele, C., Spadaro, D., Poletto, G., Livi, S., von der Lühe, O., Geiss, J., Timothy, J.G., Gloeckler, G., Allegra, A., Basile, G., Brusa, R., Wood, B., Siegmund, O.H.W., Fowler, W., Fisher, R., Jhabvala, M.: 1995, Solar Phys. 162, 313.
Rogerson, J.B., Spitzer, L., Drake, J.F., Dressler, K., Jenkins, E.B., Morton, D.C., York, D.G.: 1973, Astrophys. J. 181, L97.
Romoli, M., Frazin, R.A., Kohl, J.L., Gardner, L.D., Cranmer, S.R., Reardon, K., Fineschi, S.: 2002, In: Pauluhn, A., Huber, M.C.E., von Steiger, R. (eds.) The Radiometric Calibration of SOHO, ISSI Scientific Report SR-002, 181.
Siegmund, O.H.W., Stock, J.M., Marsh, D.R., Gummin, M.A., Raffanti, R., Hull, J., Gaines, G.A., Welsh, B.Y., Donakowski, B., Jelinsky, P.N., Sasseen, T., Tom, J.L., Higgins, B., Magoncelli, T., Hamilton, J.W., Battel, S.J., Poland, A.I., Jhabvala, M.D., Sizemore, K., Shannon, J.: 1994, Proc. SPIE 2280, 89.
Taylor, B.N., Kuyatt, C.E.: 1994, Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results, NIST Technical Note 1297, U.S. Government Printing Office. See also Wyatt, C.L., Privalsky, V., Datla, R.: 1998, Recommended Practice; Symbols, Terms, Units, and Uncertainty Analysis for Radiometric Sensor Calibration, NIST Handbook 152 (Appendix 2), U.S. Government Printing Office. The combined standard uncertainty is taken to represent the estimated standard deviation in the result.
Author information
Authors and Affiliations
Corresponding author
Additional information
B. Valcu now at BrainLAB, Inc, 3 Westbrook Corporate Ctr., Tower 3, Suite 400, Westchester, IL 60154, USA, e-mail: bogdan.valcu@brainlab.com or Bogdan_valcu@hotmail.com
Rights and permissions
About this article
Cite this article
Valcu, B., Smith, P.L., Gardner, L.D. et al. Tracking UVCS/SOHO Responsivity with Observations of ζ Tau. Sol Phys 243, 93–104 (2007). https://doi.org/10.1007/s11207-007-0377-5
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11207-007-0377-5