Orbital Pegasus - Manual (Page 67)

Release 7.0 Apr 2010 56
Pegasus User’s Guide
Prior to each flight, Orbital evaluates the
interaction of the flight MDL with the mission-
independent guidance and control software in the
Guidance and Control Laboratory (GCL). Orbital
personnel conduct a formalized series of
perturbed trajectories, representing extreme
disturbances, to ensure that both the flight MDL
and the G&C software are functioning properly.
MDL performance is judged by the ability of the
simulation to satisfy final stage burnout
requirements. The final flight MDL verification is
obtained by conducting a closed-loop, real-time
simulation.
8.3.10. Post-Launch Analysis
Orbital provides a detailed mission report to the
customer normally within 6 weeks of launch.
Included in the mission report is the actual
trajectory, event times, environments, and other
pertinent data as reduced from telemetry from on-
board sensors and range tracking. Orbital also
analyzes telemetry data from each launch to
validate Pegasus’ performance.
8.4. Interface Design and Configuration
Control
Orbital develops a mission-unique payload ICD to
succinctly define the interface requirements for the
payload. This document details mechanical,
electrical, and environmental interfaces between
the payload and Pegasus as well as all payload
integration specifics, including GSE, interface
testing, and any unique payload requirements.
The customer and Orbital jointly approve the ICD.
8.5. Mission Planning Schedule
Orbital develops a MPS tailored to each mission’s
schedule requirements. The MPS is a dynamic
document used to support the MIWG planning and
scheduling process. In conjunction with the MPS,
a detailed (day-to-day) integration schedule is
used at the integration and launch site to schedule
and coordinate vehicle and payload activities.
8.6. Payload Documentation Support
The timely and accurate delivery of payload
information is imperative in support of a number of
Orbital’s documents and analyses. Coordination
of these deliverables is provided for in the MIWG
process and tracked in the MPS.
9. SHARED LAUNCH ACCOMMODATIONS
Orbital has extensive experience in integrating and
launching multiple payloads. Multiple spacecraft
configurations have been flown on a number of
Pegasus missions to date.
Two technical approaches are available for
accommodating multiple payloads. These design
approaches are:
 Load-Bearing Spacecraft — aft spacecraft
designed to provide the structural load path
between the forward payload and the launch
vehicle, maximizing utilization of available
mass performance and payload fairing volume
 Non-Load-Bearing Spacecraft — aft
spacecraft whose design cannot provide the
necessary structural load path for the forward
payload
9.1. Load-Bearing Spacecraft
Providing a load-bearing aft payload maximizes
use of available volume and mass. The available
mass for the aft payload is determined by the
Pegasus performance capability to orbit less the
forward payload and attach hardware mass. All
remaining mission performance, excluding a stack
margin, is available to the aft payload. The load-
bearing spacecraft interfaces directly to Pegasus
and the forward payload via pre-determined
interfaces. These interfaces include standard
Orbital separation systems and pass-through
electrical connectors to service the forward
payload. Figure 9-1 illustrates this approach.