A choice within an alias represents a high-level
configuration option. For example, some missions
may require either a single 70-meter antenna, or two
or more arrayed 34-meter antennas. Each of these
possibilities corresponds to very different antenna
selections, while still satisfying the requirements of
the overall service specification. Within a choice, all
acceptable sets of antennas/equipment combinations
must be specified, in preference order (if applicable).
Antenna/equipment combinations within a single
antenna choice are in the form of a single list, while
those in array choices contain multiple such lists.
The same antenna may play different roles within
these options, for example as a reference or slave
antenna depending on how the equipment is to be
Depending on the nature of the activity, different
times must be scheduled for the activity setup (before
tracking starts) and teardown (after it completes).
Typical setup times are 30 to 90 minutes, while teardown times are usually shorter. The alias definition
specifies the default (minimum) setup and teardown
time for each antenna/equipment option. In special
circumstances these times may be lengthened, but
may not be shortened without violating DSN operational rules (and causing a setup or teardown conflict).
Once aliases are defined and validated, their usage
in DSE is straightforward. Whenever a user creates a
scheduling requirement, a service alias must be specified. The selected alias then determines all the
remaining DSN asset requirements and options,
while the remainder of the requirement goes on to
specify parameters such as timing, duration, and
relationships to other tracks. By separating the definition of aliases from their usage, it becomes easier to
validate them to ensure that any selection is a legal
DSN configuration for that service user.
Setup Teardown Act. descript
... ... ... ...
30m 15m TKG PASS
TKG PASS 30m 15m
1h 15m 15m
30m 15m ARY S
DSS- 14 (N007)
VGRI – Service Alias “TTC v0”
Choice 1: Simple
1 x 70m antenna
Examples of alternative track instantiations
for the same total tracking duration
Viewperiods: TX LO
Choice 2: Array
2 x 34m antenna
DSS-15 (N519) DSS- 24 (N011)
DSS- 14 (N007) TKG PASS
teardown DSS-24/N011 ARY S
teardown DSS-15/N519 ARY R24
Figure 5. An Illustration of the Structure of a Service Alias Representing a Choice Between a
Single Antenna and Multiple Antenna (Array) Implementation of the Same Tracking Duration.
Red highlights the information related to a single-track choice (left) and blue that related to a two-antenna array choice (right). More complex aliases are used to represent up to four station arrays, specialized ranging tracks (DDOR), separate uplink and downlink options for
multiple spacecraft tracked all at once, and maintenance activities that affect an entire complex or the entire DSN at once.