[vsnet-grb 11165] Correction to Sun/Moon Calculations for delayed notices

[Bacodine]

TO:  All GCN Sites                                20 Nov 05(*)
RE:  Correction in Sun/Moon calculations

OLD and NEW WAY:
Up till now, the GCN program has been using the TJD and Sec-of-Day
for the burst when calculating the RA,Dec of the Sun & Moon and
for the Moon illumination.  This worked fine in the early days of GCN
when ALL the messages were created in real-time (ie received and
distributed with 1-30 sec after the burst, depending on the source type),
but as time progressed  messages started to occur that were delayed in creation
(ie hours after the original burst).  During this delay,
the Sun and the Moon move (especially the Moon), so the Sun_distance,
Moon_distance, and Moon_illumination change from those values
at the time of the burst.  Now the program uses the values
at the time of issuing the notice (not the time of the burst)
no matter what the delay (seconds, minutes, hours, or even days).

WHICH NOTICES WERE AFFECTED:
The Notices that have substantial delay between the 'burst time'
and the 'issuance time' are the <any_mission>-Retractions and
the HETE Ground_Analysis Notices.  The delays are typically 1-6 hours.
The INTEGRAL TEST Notices also suffer this problem because they are issued
with a fixed TJD and SOD, so as the year progresses, the delay can become
up to months.  This is not so much of a problem, because they are Test Notices
(not real burst notices), but people may get confused if they look closely
at the Sun/Moon RA,Dec positions and the Moon Illumination (eg 6 months
makes a big difference in the Sun position).

ACKNOWLEDGEMENT:
I thank Arne Henden for pointing out the descrepancy in the Sun/Moon positions
in these delayed Notices.



REQUESTS FOR CONFIG CHANGES:
People can take this opportunity to request changes in your configuration
(your current config is appended below).
Send those requests to:
   scott at milkyway.gsfc.nasa.gov
(Replies to this announcement's email_address go to another place and
will not be noticed for many days-weeks.)  And when requesting a change
to your configuration, please include your sitename.  Just put a marker
next to the items in your configuration (appended below) that you want changed.


Sincerely,

Scott Barthelmy                      NASA-GSFC, Code 661, Greenbelt, MD   20771
PHONE:  301-286-3106                 (office)
PHONE:  301-346-3733                 (cell)
FAX:    301-286-1684                 (1st choice,  -1682 2nd choice)
EMAIL:  scott at lheamail.gsfc.nasa.gov
PAGER:  3013463733 at mobile.att.net    (by email, 200 characters max per message)
WEB:    http://gcn.gsfc.nasa.gov/gcn

(*)  Happy Swift Anniversery. The launch was 1 year ago today.


///////////////////////// your current configuration ///////////////////////////

Site_name: VSNET
Lon,Lat=  135.75   35.00
Distribution_method: EMAIL  Attachment_format: NONE
Address: vsnet-grb at kusastro.kyoto-u.ac.jp   
Filter:  ALL
Error_limit=   360.100 [deg, diameter]
Delta_T_limit= 999.900 [hr]
Swift_Trigger_ID_filter:   Disabled
Sources & Notice Types/Subtypes:
    RXTE-PCA_Alert_wont:     Enabled
    RXTE-PCA_Alert_will:     Enabled
    RXTE-PCA_nosaw:          Enabled
    RXTE-PCA_saw:            Enabled
    RXTE-ASM:                Enabled
    IPN_POS:                 Enabled
    ALEXIS:                  Enabled
    RXTE-ASM_TRANS:          Enabled
    HETE_S/C_ALERT:          Enabled
    HETE_S/C_UPDATE:         Enabled
    HETE_S/C_LAST:           Enabled
    HETE_GND_ANA:            Enabled
    HETE_Test_notices:       Disabled
    Test_type2_notices:      Disabled
    INTEGRAL_Test_notices:   Disabled
    SWIFT_Test_notices:      Disabled
    INTEGRAL_POINTDIR:       Disabled
    INTEGRAL_SPIACS:         Enabled
    INTEGRAL_WAKEUP:         Enabled
    INTEGRAL_REFINED:        Enabled
    INTEGRAL_OFFLINE:        Enabled
    SWIFT_BAT_GRB_ALERT:     enabled
    SWIFT_BAT_GRB_POS:       enabled
    SWIFT_BAT_GRB_POS_NACK:  enabled
    SWIFT_BAT_GRB_LIGHTCURVE:enabled
    SWIFT_FOM_2OBS:          enabled
    SWIFT_SC_2SLEW:          enabled
    SWIFT_XRT_POS:           enabled
    SWIFT_XRT_POS_NACK:      enabled
    SWIFT_XRT_SPECTRUM:      enabled
    SWIFT_XRT_IMAGE:         enabled
    SWIFT_XRT_LIGHTCURVE:    enabled
    SWIFT_UVOT_IMAGE:        enabled
    SWIFT_UVOT_SRCLIST:      enabled
    SWIFT_UVOT_POS:          enabled
    SWIFT_BAT_GRB_LC_PROC:   enabled
    SWIFT_XRT_SPECTRUM_PROC: enabled
    SWIFT_XRT_IMAGE_PROC:    enabled
    SWIFT_UVOT_IMAGE_PROC:   enabled
    SWIFT_UVOT_SRCLIST_PROC: enabled
    SWIFT_FULL_DATA_INIT:    enabled
    SWIFT_FULL_DATA_UPDATE:  enabled
    SWIFT_POINTDIR:          enabled
    SWIFT_BAT_TRANS:         Disabled


When requesting changes to your configuration,
it helps if you refer to your site_name.