# 
#                             BATSE Exposure Table
# 
# The exposure table specifies the fraction of the time that a burst at a
# particular point on the sky is detectable by BATSE, and accounts for earth
# blockage, SAA passages, times when the burst trigger is disabled, and times
# when a burst readout is in progress. It is a function of declination only.
# The burst is assumed bright enough to exceed the trigger threshold. A
# separate efficiency correction must also be included in analysis of burst
# rates as a function of peak flux. This efficiency is provided in a separate
# table; work is in progress to improve the efficiency calculation by
# including atmospheric scattering and handling of telemetry gaps.
# 
# Due to the failure of the GRO tape recorders and the presence of telemetry
# gaps in the post-1B data, a different algorithm was used in preparing this
# table than was used for the 1B catalog. The new algorithm not only handles
# telemetry gaps, but is also more accurate in computing SAA passages. In
# addition, the old algorithm excluded time intervals during which the trigger
# thresholds were not at their standard settings of 5.5 sigma in each trigger
# timescale, while the current algorithm does not. A separate table is
# provided that specifies the history of the trigger thresholds. The
# recomputed 1B exposure is higher (0.42 versus 0.38), due primarily to the
# inclusion of times when thresholds were not at 5.5 sigma. The galactic
# dipole moment of the sky exposure has changed by about 0.005, due primarily
# to the more accurate accounting for the SAA. The change in the galactic
# quadrupole moment is negligable.
# 
# In the exposure table below, the declination is given in degrees, and the
# exposure fraction at that declination is given for each of the cumulative
# catalogs (1B through 4B), and for each subset that was added to make the
# next catalog. In the previous exposure tables, the exposure was an average
# over a range of declinations of typically about 10 degrees. Here, the
# exposure applies to a specific declination. 
# 
# Additional statistics are provided at the end of the table. The average
# exposure is the average over the sky of the declination-dependant exposure
# fraction. Total time is the time between the start and the end of the
# catalog subset, in units of 10^6 seconds. Total exposure, the product of the
# previous two numbers, is the total time, in units of 10^6 seconds and
# averaged over the sky, that BATSE was sensitive was sensitive to bursts for
# that catalog subset. The values of < cos(theta) > and < sin^2(b) > - 1/3 are
# the galactic dipole and quadrupole moments of the exposure. The values of <
# sin(dec) > and < sin^2(dec) > - 1/3 are the dipole and quadrupole moments in
# the equatorial coordinate system.
# 
# The uncertainty in the exposure fractions are roughly estimated at about 4%.
# Possible sources of systematic error in the moments are currently under
# study, but are expected to be less than 0.003 for the galactic moments.
# ----------------------------------------------------------------------------
#                                   Exposure
# 
#      dec     1B       2B-1B     3B-2B      4B-3B       3B        4B
#           exposure  exposure   exposure  exposure   exposure  exposure
# 
#      ------------------------------------------------------------------
      -90  0.45553   0.49902    0.53548   0.52248    0.50389   0.51041
 
      -85  0.45542   0.50579    0.53603   0.52286    0.50609   0.51198
 
      -80  0.47268   0.51779    0.55297   0.54599    0.52167   0.53020
      -75  0.47837   0.53424    0.56566   0.55382    0.53363   0.54072
 
      -70  0.47336   0.53057    0.56145   0.54889    0.52938   0.53622
 
      -65  0.46557   0.52308    0.55318   0.54085    0.52146   0.52827
 
      -60  0.45694   0.51377    0.54320   0.53163    0.51203   0.51891
 
      -55  0.44766   0.50368    0.53235   0.52180    0.50181   0.50882
 
      -50  0.43768   0.49225    0.52018   0.51085    0.49043   0.49759
 
      -45  0.42658   0.47904    0.50546   0.49780    0.47710   0.48436
      -40  0.41195   0.46345    0.49015   0.48016    0.46189   0.46830
 
      -35  0.40406   0.45560    0.48185   0.47065    0.45382   0.45973
 
      -30  0.39899   0.45045    0.47646   0.46457    0.44859   0.45420
 
      -25  0.39556   0.44697    0.47284   0.46047    0.44506   0.45047
 
      -20  0.39329   0.44468    0.47050   0.45775    0.44275   0.44801
 
      -15  0.39193   0.44333    0.46917   0.45610    0.44141   0.44656
      -10  0.39133   0.44279    0.46869   0.45536    0.44088   0.44596
       -5  0.39141   0.44296    0.46898   0.45543    0.44108   0.44611
        0  0.39214   0.44382    0.47000   0.45626    0.44198   0.44699
 
        5  0.39352   0.44537    0.47178   0.45786    0.44358   0.44859
 
       10  0.39560   0.44765    0.47435   0.46028    0.44594   0.45097
 
       15  0.39845   0.45076    0.47782   0.46361    0.44914   0.45422
 
       20  0.40222   0.45484    0.48234   0.46803    0.45334   0.45850
 
       25  0.40714   0.46013    0.48820   0.47381    0.45878   0.46406
 
       30  0.41358   0.46701    0.49580   0.48141    0.46587   0.47133
 
       35  0.42227   0.47618    0.50597   0.49170    0.47536   0.48109
 
       40  0.43490   0.48917    0.52052   0.50682    0.48895   0.49522
 
       45  0.45731   0.51329    0.54609   0.53375    0.51327   0.52045
 
       50  0.47454   0.53442    0.56864   0.55250    0.53401   0.54050
       55  0.48814   0.55085    0.58588   0.56754    0.55006   0.55620
       60  0.50004   0.56440    0.60046   0.58048    0.56364   0.56955
       65  0.51062   0.57654    0.61348   0.59207    0.57577   0.58149
 
       70  0.51995   0.58646    0.62448   0.60197    0.58601   0.59161
       75  0.52689   0.59336    0.63238   0.60909    0.59337   0.59889
 
       80  0.52581   0.58562    0.62876   0.60688    0.58920   0.59540
 
       85  0.51748   0.58184    0.62256   0.59335    0.58315   0.58673
 
       90  0.51965   0.57835    0.62349   0.59353    0.58311   0.58677
 
#      ------------------------------------------------------------------
# 
#        ------------------------------------------------------------
# 
#                              1B   2B-1B 3B-2B   4B-3B     3B    4B
# 
#         ------------------------------------------------------------
# 
#         Average Exposure
#         factor            0.425   0.478  0.507 0.494   0.477  0.483
# 
#         Total Time
#         (10^6s)            27.9   31.1    49.1  61.36 108.1   171.5
# 
#         Total
#         Exposure(10^6s)   12.05    14.9   24.9 30.31    51.6  81.9
# 
#         No. of bursts       260    325     537    515  1122   1637
# 
#         < cos(theta) >    -0.008 -0.009 -0.009 -0.008 -0.009  -0.009
# 
#         < sin^2(b) > -
#         1/3               -0.004 -0.004 -0.004 -0.004 -0.004  -0.004
# 
#         < sin(dec) >      0.017  0.018   0.019  0.017 0.018   0.018
# 
#         < sin^2(dec) > -
#         1/3               0.025  0.024   0.024  0.024 0.024   0.024
# 
#         ------------------------------------------------------------
# ----------------------------------------------------------------------------