Star Counts. M.Lampton Sept 2002 Updated Sept 2003. Motivation. Can SNAP guide itself satisfactorily? Are there enough guide stars? bright enough for low photon shot noise numerous enough so that a reasonable size guider field is 99.99+% certain to get a star.
Updated Sept 2003
Coarse star trackers
Coarse sun sensors
focal plane guider
Environment: orbit, Sun, Earth, stars....
What is the disturbance torque spectrum?
What are the various sensor noise spectra?
What is the closed-loop response?
Aldering Region in GSC 2.2RA=244.0, dec=+55.0DeltaRA=8.75deg, DeltaDec=1.5degon sky: 5.0 deg x 1.5 deg = 7.5sqdegGSC 2.2, DPOSS IIR “F” band=IIIaF+RG610= 0.65umhttp://www-gsss.stsci.edu/support/data_access.htm15512 “objects”all non-stars, Kodak objects etc rejected
B&S: Bahcall & Soneira, Ap.J.Supp. v.55, 67-99 1984
Allen: C.W.Allen "Astrophysical Quantities" Third edition 1973 p.243
Basel: Bahcall et al, Ap.J. v.299 p.616-632, 1985
SDSS: Newberg Richards Richmond & Fan, "Catalog of four color photometry...” 2002 see also... Chen et al, ApJ v.553, pp.184-197, 2001
EDD: http://star-www.st-and.ac.uk "EDDINGTON Cumulative Star Counts"
M&S: O.Yu.Malkov & O.M.Smirnov, "Testing the Galaxy Model with GSC" ADASS III ASP Conf. v.61 1994.
GEMINI: http://www.shef.ac.uk/cgi-bin-cgiwrap/phys/compstars.ps Doug Simms Aug 1995 "Longitudinally Averaged Cumulative Star Counts"
Front illuminated CCDs:
typical QE ~ 30%
typical BW ~ 400nm
typical QE*BW ~100 to 200nm
Guider CCDs located within rear metering structure, on optical axis