Status Report

Alternate Access To Station (AAS) Performance Requirements Document International Space Station

By SpaceRef Editor
May 12, 2004
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Alternate Access To Station (AAS) Performance Requirements Document International Space Station

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February 15, 2002

Contract NAS9-20000

Space Flight Operations Contract USA004882



This document identifies the basic functional performance requirements that an
Alternate Access to Station System, hereafter termed AAS, is expected to satisfy to
perform logistics resupply for the orbiting International Space Station (ISS). It has been
developed to provide potential AAS service providers with information to support
development of end-to-end AAS concepts.

This document is not intended to and does not serve as the set of detailed design and
functional requirements necessary to develop such a system.


The requirements in this document are based on analysis of potential cargos and
existing operational rules and criteria. They have been developed to maximize the
potential use of the AAS while minimizing the design and cost impact of infrequent or
unique cargo items and operational scenarios. Some of the criteria (e.g., power
available from the ISS) have been developed based on standardized or normalized ISS
allocations with the recognition that the actual specification or Interface Control
Document (ICD) limits will be negotiated with the ISS program during the detailed
design phase. Those using this document are encouraged to better the criteria rather
than depending on negotiated accedences, thereby developing an AAS that is of
greater value to the ISS. This document shall not be construed as a commitment by the
ISS Program to use any system that satisfies these requirements.

This document provides the following:

a. Basic conceptual requirements

b. Standardized cargo descriptions

c. Cargo processing considerations

d. Representative mission definitions

e. Other ISS interface considerations

The requirements herein have been developed assuming no use of International
Partner (IP) assets.


The following reference requirements are intended to ensure that AAS concepts are
compatible with the existing ISS design, operations, and utilization concepts and
constraints. Deviations from these requirements may have significant implications on
the viability of the resulting concept.

2.1 The AAS orbital transfer element will be unmanned.

2.2 The AAS will support the ISS altitude profile from 278 to 460 km
(150 to 248 n. mi.) at an inclination of 51.6 degrees.

2.3 The AAS will not require changes to the ISS that adversely affect the ISS
performance or capabilities. The AAS will not adversely impact other
vehicles that interface with the ISS.

2.4 The AAS service provider is responsible for the purchase and integration of
hardware to their vehicle to be compatible with the ISS (e.g., Common
Berthing Mechanism (CBM), Flight Releasable Grapple Fixture (FRGF),
Power Data Grapple Fixture (PDGF), passive Flight Releasable Attachment
Mechanism (FRAM), etc.).

2.5 The AAS orbital transfer element will be required to perform all maneuvers
necessary to berth/dock to the on-orbit ISS at the attitudes defined in
SSP 50261-01, Generic Groundrules, Requirements and Constraints.

2.6 The AAS will not provide ISS propellant delivery services.

2.7 The AAS will not provide attitude control or ISS reboost while attached to
the ISS.

2.8 The AAS orbital transfer element will have a space-to-space
communication system compatible with the ISS for the purpose of relaying
command and data telemetry.

2.9 The AAS orbital transfer element will have a Guidance, Navigation and
Control (GN&C) system commandable from the ISS while in proximity

2.10 External cargo transfers between the AAS orbital transfer element and the
ISS will be performed via Extravehicular Robotics (EVR), not by
Extravehicular Activity (EVA).

2.11 The ISS can provide resources to the AAS vehicle, depending on the
mating location, while the vehicle is attached to the ISS. These resources
include electrical power, atmospheric temperature and humidity control,
Command and Data Handling (C&DH), and thermal cooling fluids.
Resource demand shall not be in excess of those available at a specific
interface, and specific allocation will be negotiated with the ISS Program
during the detailed design.

2.12 The AAS service provider will be responsible for providing the launch and
landing sites for their vehicle and providing the necessary facilities for cargo
integration and cargo de-integration of the vehicle that meet the cargo ground handling and environmental requirements.

2.13 In the operational phase, the ISS Program will determine the dates for AAS
attached operations and time constraints for returnable cargo.

2.14 The AAS must be capable of delivering cargo to the ISS on any date
defined by the ISS Program. It will be available year round.

2.15 Other than nominal approach and departure trajectories, the AAS vehicle
will not perform formation flight with the ISS.

2.16 The post assembly complete configuration of the ISS will reflect the
Assembly Sequence, Revision F baseline with the exclusion of the
Propulsion Module. See Figure 2-1. The ISS elements included are listed

  • All truss elements
  • Columbus Operating Facility (COF)
  • Japanese Experiment Module (JEM)
  • Centrifuge Accommodation Module (CAM)
  • Node 3
  • Crew Return Vehicle (CRV)
  • Hab Module
  • Russian Segment with Science Power Platform (SPP)

Additional detailed requirements are defined in subsequent sections of this document.

SpaceRef staff editor.