Springer Nature is making Coronavirus research free. View research | View latest news | Sign up for updates

XUV Photometer System (XPS): Overview and Calibrations


The solar soft X-ray (XUV) radiation is highly variable on both short-term time scales of minutes to hours due to flares and long-term time scales of months to years due to solar cycle variations. Because of the smaller X-ray cross sections, the solar XUV radiation penetrates deeper than the extreme ultraviolet (EUV) wavelengths and thus influences the photochemistry and ionization in the mesosphere and lower thermosphere. The XUV Photometer System (XPS) aboard the Solar Radiation and Climate Experiment (SORCE) is a set of photometers to measure the solar XUV irradiance shortward of 34 nm and the bright hydrogen emission at 121.6 nm. Each photometer has a spectral bandpass of about 7 nm, and the XPS measurements have an accuracy of about 20%. The XPS pre-flight calibrations include electronics gain and linearity calibrations in the laboratory over its operating temperature range, field of view relative maps, and responsivity calibrations using the Synchrotron Ultraviolet Radiation Facility (SURF) at the National Institute of Standards and Technology (NIST). The XPS in-flight calibrations include redundant channels used weekly and underflight rocket measurements from the NASA Thermosphere-Ionosphere-Mesosphere-Energetics-Dynamics (TIMED) program. The SORCE XPS measurements have been validated with the TIMED XPS measurements. The comparisons to solar EUV models indicate differences by as much as a factor of 4 for some of the models, thus SORCE XPS measurements could be used to improve these models.

This is a preview of subscription content, log in to check access.


  1. Brasseur, G. and Solomon, S.: 1986, Aeronomy of the Middle Atmosphere: Chemistry and Physics of the Stratosphere and Mesosphere, D. Reidel, Dordrecht, Boston.

  2. Canfield, L. R. and Swanson, N.: 1987, J. Res. Natl. Bureau Standards 92, 97.

  3. Canfield, L. R., Kerner, J., and Korde, R.: 1989, Appl. Opt. 28, 3940.

  4. Canfield, L. R., Vest, R., Woods, T. N., and Korde, R.: 1994, SPIE Proc. 2282, 31.

  5. Chamberlain, J. W.: 1978, Theory of Planetary Atmospheres: An Introduction to Their Physics and Chemistry, Academic Press, New York.

  6. Chamberlin, P. C., Woods, T. N., and Eparvier, F. G.: 2004, SPIE Proc. 5538, 31.

  7. Fontenla, J. M., White, O. R., Fox, P. A., Avrett, E. H., and Kurucz, R. L.: 1999, Astrophys. J. 518, 480.

  8. Henke, B. L., Gullikson, E. M., and Davis, J. C.: 1993, At. Data Nucl. Data Tables 54, 181.

  9. Hinteregger, H. E., Fukui, K., and Gilson, G. R.: 1981, Geophys. Res. Lett. 8, 1147.

  10. Judge, D. L., McMullin, D. R., Ogawa, H. S., Hovestadt, D., Klecker, B., Hilchenbach, M., Mobius, E., Canfield, L. R., Vest, R. E., Watts, R., Tarrio, C., Kuehne, M., and Wurz, P.: 1998, Solar Phys. 177, 161.

  11. Korde, R. and Canfield, L. R.: 1989, SPIE Proc. 1140, 126.

  12. Korde, R. and Geist, J.: 1987, Appl. Opt. 26, 5284.

  13. Korde, R., Canfield, L. R., and Wallis, B.: 1988, SPIE Proc. 932, 153.

  14. Lean, J.: 1987, J. Geophys. Res. 92, 839.

  15. Lean, J.: 1991, Rev. Geophys. 29, 505.

  16. Lean, J. L., Livingston, W. C., Heath, D. F., Donnelly, R. F., Skumanich, A., and White, O. R.: 1982, J. Geophys. Res. 87, 10307.

  17. Lean, J. L., Warren, H. P., Mariska, J. T., and Bishop, J.: 2003, J. Geophys. Res. 108, 1059, doi: 10.1029/ 2001JA009238.

  18. Meier, R. R., Warren, H. P., Nicholas, A. C., Bishop, J., Huba, J. D., Drob, D. P., Lean, J., Picone, J. M., Mariska, J. T., Joyce, G., Judge, D. L., Thonnard, S. E., Dymond, K. F., and Budzien, S. A.: 2002, Geophys. Res. Lett. 29, doi: 10.1029/2001GL013956.

  19. Mewe, R. and Gronenschild, E. H. B. M.: 1981, Astron. Astrophys. Suppl. Ser. 45, 11.

  20. Mewe, R., Gronenschild, E. H. B. M., and van den Oord, G. H. J.: 1985, Astron. Astrophys. Suppl. Ser. 62, 197.

  21. Mewe, R., Lemen, J. R., and van den Oord, G. H. J.: 1986, Astron. Astrophys. 65, 511.

  22. Pap, J. M., Fröhlich, C., Hudson, H. S., and Solanki, S. K. (eds.): 1994, The Sun as a Variable Star: Solar and Stellar Irradiance Variations, Cambridge University Press, Cambridge.

  23. Parr, A. C. and Ebner, S.: 1987, SURF II User Handbook, NBS Special Publication, Gaithersburg, MD.

  24. Powell, F. R., Vedder, P. W., Lindblom, J. F., and Powell, S. F.: 1990, Opt. Eng. 26, 614.

  25. Richards, P. G., Fennelly, J. A., and Torr, D. G.: 1994, J. Geophys. Res. 99, 8981.

  26. Rottman, G. J.: 1987, in P. Foukal, (ed.), Solar Radiative Output Variation, Cambridge Research and Instrumentation Inc., Boulder, Colorado, p. 71.

  27. Scholze, F., Thornagel, R., and Ulm, G.: 2001, Metrologia 38, 391.

  28. Tobiska, W. K.: 1991, J. Atmos. Terr. Phys. 53, 1005.

  29. Tobiska, W. K.: 1993, J. Geophys. Res. 98, 18879.

  30. Tobiska, W. K. and Barth, C. A.: 1990, J. Geophys. Res. 95, 8243.

  31. Tobiska, W. K. and Eparvier, F. G.: 1998, Solar Phys. 177, 147.

  32. Tobiska, W. K., Woods, T. N., Eparvier, F. G., Viereck, R., Floyd, L., Bouwer, D., Rottman, G. J., and White, O. R.: 2000, J. Atmos. Sol.-Terr. Phys. 62, 1233.

  33. Walker, J. H., Saunders, R. D., Jackson, J. K., and McSparron, D. A.: 1988, J. Res. Natl. Bureau Standards 93, 7.

  34. Warren, H. P., Mariska, J. T., and Lean, J.: 1998a, J. Geophys. Res. 103, 12077.

  35. Warren, H. P., Mariska, J. T., and Lean, J.: 1998b, J. Geophys. Res. 103, 12091.

  36. Warren, H. P., Mariska, J. T., and Lean, J.: 2001, J. Geophys. Res. 106, 15745.

  37. White, O. R. (ed.): 1977, The Solar Output and Its Variation, Colorado Associated University Press, Boulder.

  38. Woods, T.: 1992, in D. Donnelly (ed.), Working Group 4 and 5 Report for 1991 SOLERS 22 Workshop, Proc. of SOLERS 22 Workshop, NOAA, Boulder, Colorado, pp. 460–467.

  39. Woods, T. N. and Rottman, G. J.: 1990, J. Geophys. Res. 95, 6227.

  40. Woods, T. N. and Rottman, G. J.: 2002, in M. Mendillo, A. Nagy, and J. Hunter Waite, Jr. (eds.), Comparative Aeronomy in the Solar System, Geophysics Monograph Series, Washington, DC, pp. 221–234.

  41. Woods, T. N. and Rottman, G. J.: 2005, Solar Phys., this volume.

  42. Woods, T., Eparvier, F., Bailey, S., Solomon, S. C., Rottman, G., Lawrence, G., Roble, R., White, O. R., Lean, J., and Tobiska, W. K.: 1998, SPIE Proc. 3442, 180.

  43. Woods, T., Rodgers, E., Bailey, S., Eparvier, F., and Ucker, G.: 1999a, SPIE Proc. 3756, 255.

  44. Woods, T., Rottman, G., Russell, C., and Knapp, B.: 1999b, Metrologia 35, 619.

  45. Woods, T. N., Acton, L. W., Bailey, S., Eparvier, F., Garcia, H., Judge, D., Lean, J., McMullin, D., Schmidtke, G., Solomon, S. C., Tobiska, W. K., and Warren, H. P.: 2004, in J. Pap, C. Fröhlich, H. Hudson, J. Kuhn, J. McCormack, G. North, W. Sprig, and S. T. Wu (eds.), Solar Variability and Its Effect on Climate, Geophysics Monograph Series, 141, Washington, DC, pp. 127–140.

Download references

Author information

Correspondence to Thomas N. Woods.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Woods, T.N., Rottman, G. & Vest, R. XUV Photometer System (XPS): Overview and Calibrations. Sol Phys 230, 345–374 (2005).

Download citation


  • Lower Thermosphere
  • Solar Cycle Variation
  • Spectral Bandpass
  • Rocket Measurement
  • Redundant Channel