Orbital Pegasus - Manual (Page 74)

Release 7.0 Apr 2010 63
Pegasus User’s Guide
and the avionics section also alters the maximum
expected shock response spectrum at the base of
the payload. Environmental levels for a vehicle
configured with HAPS will be provided on a
mission-specific basis.
10.12. Load Isolation System
Authorize by: L-24 months
Orbital can provide a Load Isolation System that
will lower the fundamental frequencies of the pay-
load to avoid dynamic coupling with the Pegasus
fundamental frequencies at drop. This Load Isola-
tion System will decrease volume and mass avail-
able to the payload, to be quantified by the fre-
quency modification requirements of the payload.
10.13. Low Tip-Off Rate with Reduced Clamp
Band Tension
Authorize by: L-12 months
For payloads that are significantly below the
structural capabilities of the separation system,
Orbital can perform analysis to verify system
structural capability and coupled loads model
analysis of clamp band with reduced Marmon
clamp tension in order to reduce payload tip-off.
Clamp band separation impulse is one of the
primary causes of tip-off on the Pegasus separa-
tion system, and reduced clamp band tension will
reduce the tip-off from clamp band release propor-
tionally. Testing will be performed if required to
validate the analysis results. This tip-off reduction
technique can be performed with the 97 cm
(38 in.), 59 cm (23 in.), or 43 cm (17 in.) PA.
10.14. Enhanced Telemetry Capabilities –
Payload Data
Authorize by: L-20 months
Orbital offers a payload Serial Telemetry Interface
that is used to incorporate payload telemetry and
state of health data into Pegasus launch vehicle
telemetry. This interface may be either a 4-wire
RS-422 or a 2-wire RS-485 serial communication
link between the Pegasus flight computer and the
spacecraft. The interface uses a poll/response
protocol. The Pegasus flight computer polls the
payload at a 1 Hz rate and receives a pre-
determined block of payload data to be
incorporated into the launch vehicle telemetry
stream. The payload telemetry data volume
cannot exceed 250 bytes/sec. As part of this
nonstandard service, Orbital can incorporate two
text-based and one graphical-based data display
pages into Pegasus telemetry software to display
this payload data in the launch control facility
during ground operations, captive carry, and
powered flight. Orbital will support up to two
standalone tests with the spacecraft prior to
integrated operations as a means to verify the
interface protocol and spacecraft data format.
These tests will be performed with an EDU flight
computer.
The serial telemetry interface utilizes reserved
pins in one of the 42-pin connectors at the
separation interface and, therefore, does not affect
the capacity of the standard payload electrical
interface. The interface wiring will be documented
on a mission-specific EICD. The interface protocol
will be documented in a mission-specific serial
communication specification.
10.15. State Vector Transmission From
Pegasus
Authorize by: L-20 months
Pegasus can utilize a serial communication link
with the payload to transmit a state vector from the
flight computer directly to the satellite. This state
vector will be in a format specified in the Pegasus
Technical Document, TD-0271, Pegasus State
Vector Technical Specification. Accuracy of the
state vector will be that of the Pegasus inertial
navigation system. This service must be
exercised in conjunction with the enhanced
telemetry service described in Section 10.14.