on a rolling weekly basis. These requirements include
tracking time and services required, constraining
time intervals and relationships (for example, minimum and maximum gaps), visibility constraints, and
flexibilities. Further discussion of the nature of these
requirements and flexibilities is included in the DSN
Scheduling Requests section.
Once the deadline passes and all requirements are
in, the full set is integrated into an initial schedule in
which conflicts are reduced by taking advantage of
whatever flexibilities have been specified. This version of the schedule is extremely heavily overloaded,
but it does indicate where there are contentious time
periods. These contentious areas shift from week to
week depending on critical activities, as well as on
the slow drift of visibility intervals with time.
There follows an optimization step where an expe-
rienced DSN scheduler interactively edits the sched-
ule and further reduces conflicts by taking advantage
of unspecified flexibilities and making further adjust-
ments. At the conclusion of this phase, the schedule
usually contains fewer than 30 conflicting sets of
activities. It is then released to the scheduling user
community who negotiate to reduce conflicts and
further optimize coverage for their missions.
It is important to note that, unlike many other
scheduling domains, the DSN follows a collaborative
approach to developing the conflict-free schedule.
DSN users follow a peer-to-peer approach to resolving conflicts. Users create change proposals, which
are suggestions as to how different sets of users could
modify their tracking passes to resolve conflicts. The
affected users can concur or reject these suggestions
and counter with suggestions of their own. Over the
course of a few weeks, convergence is reached and
the schedule reaches a negotiated conflict-free status.
Should users not come to agreement among themselves, there is an escalation process to adjudicate
irreconcilable conflicts; escalation very rarely occurs
in practice. When negotiation concludes, the schedule is conflict free or has only a few waived conflicts
for specific reasons. This is considered the negotiated schedule that missions use to plan their integrated ground and spacecraft activities, including the
Figure 2. Example of an HTML5 Canvas View of a Portion of the DSN Schedule.
Mousing over a track brings up a transient window with detailed information about the activity (lower right). In this view, different missions are color coded, and setup/teardown is indicated by the black segments at the top left and right of each activity. Each time line represents one of the DSN antennas.
MSL VGR1 STF GTL KEPL DSN CAS
STA STA ST
ACE GTL SOHO
GRLB GTL DAWN WIND
Track: 2012-02-13 (044)13: 55 - 2012-02-13(044)21: 20 (7h
Activity: 2012-02-13(044)12: 55 - 2012-2-13(044)21: 35 ( 8
Mission: STA (TTC v0)
Asset: DSS- 26 (N002) CCP NMC RNG RRPA TLPA UPL X
Setup: 1h Teardown: 15m
Description: SSR DUMP/UNATT WorkCat: 1A1 SOE: A N
Time 2012/02/13 (044) 2012/02/14 (045)