Title:
Impact of Observing Constraints and Unplanned Events on
Observatory Efficiency and Long Range Plan Stability

Author: William Workman

Abstract:

In an era of increasing pressure to do more with less and make the
most out of every budget dollar, HST science operations have steadily
been able to give its customers more by increasing observing
efficiency.  While original mission goals for efficiency were
targetted at less than 35%, HST now consistently achieves average
observing efficiencies of greater than 50%. Furthermore, special
concentration on continuous viewing opportunities and science
campaigns (i.e. - the Hubble Deep Field) has yielded efficiencies
exceeding 60%. More than fourteen years of applied operational
experience and analysis of the HST ground, flight, instrument, and
user support systems have resulted in this success. However, these
efficiency levels could be even higher were it not for the variety of
constraints and unplanned events which affect how and when the
observatory can be used.

Certain known spacecraft and instrument constraints impact efficiency
with little affect on long range plan stability since they can be
accounted for in advance. For this class of concerns, planning
scenarios can be developed and analyzed to see what efficiencies might
be achieved without these constraints.

Unpredictable events such as spacecraft safings and anomalies, targets
of opportunity and directors discretionary science reduce the overall
stability of an observatory's planned use as well as its efficiency.

In this paper we will describe various constraints and unplanned
events, show their effects on HST observing efficiency and stability,
and discuss efforts by the HST Long Range Planning Group to minimize
their impact.