- COO CALTECH OPTICAL OBSERVATORIES
CALIFORNIA INSTITUTE OF TECHNOLOGY
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Date
Project Name
Scope Statement
Document Owner: Principal Investigator
This is an internal working note of Caltech Optical Observatories.
COO
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Project Scope Statement
Need(s)
Concise need statement goes here. Could be phrased positively (e.g. 'improved XYZ will
provide'), or negatively ('we are currently unable to XYZ').
Solution
Concise description of the project scope goes here. Should have sufficient detail to
convey the nature and boundaries of the project, without technical detail, nor budget or
schedule detail (these are negotiated in subsequent planning documents).
Should also indicated what is _not_ in the project, where confusion may exist (e.g. it's a
detector upgrade, but not a controller upgrade)
Revision Sheet
The revision sheet should track significant changes to the document and be consistent with
project version control numbering.
Release
No.
Rev. 0.1
Date
Revision Description
30 Nov 2004
Initial draft
Caltech
Optical
Observatories
Scope Statement
Authorization Memorandum
I have carefully reviewed the Scope Statement for the Project Name project.
MANAGEMENT CERTIFICATION - Please check the appropriate statement.
______ The document is accepted.
______ The document is accepted pending the changes noted.
______ The document is not accepted.
Notes:
We fully accept noted changes as necessary improvements and authorize initiation of work to
proceed. Based on our authority and judgment, the continued development of this subsystem
according to these Functional Requirements is hereby authorized.
_______________________________
Name
Principal Investigator
_____________________
DATE
_______________________________
Name
OIR Project Lead
_____________________
DATE
_______________________________
R. Dekany
Associate Director for Development
_____________________
DATE
FUNCTIONAL REQUIREMENTS DOCUMENT
TABLE OF CONTENTS
Page
1
General information ............................................................................................................................ 6
1.1
Purpose ....................................................................................................................................... 6
1.2
Scope ........................................................................................................................................... 6
1.3
Definitions .................................................................................................................................. 6
1.4
Acronyms and Abbreviations ................................................................................................... 6
1.5
Applicable Documents............................................................................................................... 6
1.5.1
1.5.2
1.6
2
TMT Documents .................................................................................. Error! Bookmark not defined.
Non-TMT Documents.......................................................................... Error! Bookmark not defined.
Points of Contact........................................................................................................................ 6
General description ............................................................................................................................. 7
2.1
Background ................................................................................................................................ 7
2.2
System Objectives ...................................................................................................................... 7
2.3
Product Functions ..................................................................................................................... 7
2.4
General Constraints .................................................................................................................. 7
2.5
Assumptions and Dependencies ............................................................................................... 7
2.5.1
2.5.2
2.6
3
Assumptions on Other Observatory Subsystems ................................................................................... 7
Concept of Operations ........................................................................................................................... 8
Interfaces .................................................................................................................................... 8
Requirements ....................................................................................................................................... 9
3.1
Performance Characteristics .................................................................................................. 10
3.1.1
3.1.2
3.1.3
3.1.4
3.1.5
3.1.6
3.1.7
3.1.8
3.1.9
3.1.10
3.2
3.2.1
3.2.2
3.2.3
3.2.4
Science wavelength range .................................................................................................................... 10
Unvignetted science field of view........................................................................................................ 10
Guide stars ........................................................................................................................................... 10
Technical field of view ........................................................................................................................ 10
RMS wavefront error, ensquared energy, and/or flux contrast ............................................................ 10
Strehl, encircled energy, and/or point spread function stability ........................................................... 10
Differential astrometric precision ........................................................................................................ 10
Throughput .......................................................................................................................................... 10
Emissivity ............................................................................................................................................ 10
Operational efficiency ..................................................................................................................... 10
Physical Characteristics .......................................................................................................... 10
Mass ..................................................................................................................................................... 11
Space .................................................................................................................................................... 11
Power consumption.............................................................................................................................. 11
Cooling requirements ........................................................................................................................... 11
3.3
Reliability ................................................................................................................................. 11
3.4
Maintainability ........................................................................................................................ 11
3.4.1
3.4.2
3.5
3.5.1
3.5.2
Test points............................................................................................................................................ 11
Maintenance personnel requirements................................................................................................... 11
Environmental Conditions ...................................................................................................... 11
Natural Environment............................................................................................................................ 11
Induced Environment ........................................................................................................................... 12
3.6
Shipping requirements ............................................................................................................ 12
3.7
Design and Construction ......................................................................................................... 12
3.8
Facilities Requirements ........................................................................................................... 12
3.8.1
3.8.2
Handling Tools .................................................................................................................................... 12
Lab Requirements ................................................................................................................................ 12
1 GENERAL INFORMATION
1.1 Purpose
Describe the purpose of the Functional Requirements Document and its intended audience.
1.2 Scope
Describe the subsystem or item to be produced by name
Example: Multiconjugate Adaptive Optics System (MCAO).
Explain what the subsystem will and will not do. The point is to clearly delineate functional
responsibilities of subsystems (e.g. MCAO shall provide high-speed wavefront sensor telemetry,
but is not responsible for per-observation estimation of the point spread function)
1.3 Definitions
Define all terminology used in the document so that non-experts can interpret its contents. For
example, "real-time software" is subject to interpretation. This section should make clear all
potentially ambiguous terminology in the context of this document.
1.4 Acronyms and Abbreviations
List all acronyms and abbreviations used in this document.
1.5 Applicable Documents
Provide a list of the references that were used in preparation of this document.
documents explicitly cited herein.
Identify
1.6 Points of Contact
Provide a list of the points of contact that may be needed by the document user for informational
and troubleshooting purposes. Include contact name, role, department, telephone number, and email address (if applicable). Points of contact may include, but are not limited to, engineers and
scientists that have contributed to the requirements development.
2 GENERAL DESCRIPTION
This section should describe the general factors that affect the product and its requirements. This
section does not state specific requirements, but makes those requirements easier to understand.
2.1 Background
Provide background information concerning the uses and purposes of the system. Refer to
interfacing systems when needed to enhance the general description.
2.2 System Objectives
State the major requirements and goals of the product. These statements should be concise,
quantified if possible, and may include examples. Identify products from other systems used
with the current system.
2.3 Product Functions
This section should provide a summary of the functions that the product will perform, in general
statements. Details will go into the requirements section (Section 3).
2.4 General Constraints
This section should give a general description of the constraints that will limit the designer's
options. This subsection should not be used to impose specific requirements, but rather should
provide rationale supporting requirements and specifications in Section 3.
Example: Queue scheduling of TMT observations relaxes the need for autonomous selfdiagnosis with the MCAO system. However, routine service of unit-replaceable boards shall be
scheduled only on a monthly basis.
2.5 Assumptions and Dependencies
This section should list factors that affect the requirements, i.e. certain assumptions have been
made in writing these requirements; if these change then these requirements will also need to be
changed. Identify any limitations affecting the desired capability, any desired capabilities that
will not be provided by the proposed system, and any anticipated operational changes that will
affect the proposed operation of the system.
2.5.1 Assumptions on Other Observatory Subsystems
Example: On-axis delivered wavefront error from the telescope subsystem shall be less than 2
microns peak-to-peak, less than 500 nm rms total, and less than 50nm (integrated) for spatial
frequencies less than 3m-1.
Example: We assume the MCAO system will reside in a constant-gravity environment
independent of telescope pointing.
2.5.2 Concept of Operations
This section should describe at a high level the operational concept, to the extent it impacts other
requirements in this document or issues relevant to the Systems Engineering Group.
Example: We assume here that ExAO observations will be conducted within 4 hours of a full
CO2 cleaning of the primary and secondary mirror. If this is not the case
2.6 Interfaces
For our purpose here, this section should only list the other observatory subsystems that may
require an interface to this product. This is not a technical interface specification (those will
ultimately be captured in detailed Interface Control Documents (ICDs))
Example: The MCAO system shall offload tip/tilt saturation by sending commands to repoint the
telescope (e.g. using alt and az bearings).
3 REQUIREMENTS
This section contains the specific requirements of the product to be developed. Requirements
must be:
Quantitative: Strenuous effort should be made to provide quantitative requirements. If numbers
are currently unavailable, the placeholder "TBD" , together with appropriate SI units, should be
used.
Example: GLAO shall transmit 1 - 5 um science light with transmission >90%. (Not "near
infrared")
Example: The mass of GLAO shall be TBD kg.
Unambiguous: Every requirement listed has only one interpretation. Specifications are to be
taken as firm requirements, by default (use of the word 'shall' emphasizes this, but is not
necessary). Areas of 'desired' functionality and performance shall be clearly labeled using the
term 'goal' (use of the word 'should' also indicates a desired, but not essential, specification).
Complete: All relevant requirements must be included.
Verifiable: A requirement is verifiable if and only if there exists some finite, cost-effective
process whereby the final product can be checked/tested to meet the requirement. If no method
of verification can be devised, either (1) the requirement should be eliminated, or (2) a
subsequent point in the development should be identified at which time the requirement can be
put into verifiable form (i.e. pending additional information).
Consistent: No two requirements should conflict with each other.
Non-redundant:
eliminated.
Any requirement entirely superceded by another requirement should be
Modifiable: The structure and style of this section should allow necessary changes be made
easily, completely, and consistently.
Traceable: Requirements should be both backward traceable (referencing the source of the
requirement, such as a result of specific Science Requirement or Observatory Standard) and
forward traceable (with unique numbering so as to be identified/referenced in subsequent
detailed design requirements or test documentation).
Usable during design (and relevant to operations and maintenance): Often items are modified
during the product lifecycle. The requirements should call out critical areas (such as failures that
can result in human hazard), and other information that should not be lost to maintenance
personnel.
3.1 Performance Characteristics
This section should contain all functional and performance characteristics that the product must
fulfill, i.e. what is expected of the product. If the product will be used in multiple operational
modes, the applicability of all performance characteristics to all modes should be clear.
3.1.1 Science wavelength range
Specify simultaneous and non-simultaneous delivered science bandpass.
3.1.2 Unvignetted science field of view
3.1.3 Guide stars
Should system operate on NGS, LGS, or both? Are there constraints on the NGS (e.g. highly
reddened guide stars that may require infrared wavefront sensing).
3.1.4 Technical field of view
The FoV used for both natural guide star and laser guide star acquisition (if appropriate).
3.1.5 RMS wavefront error, ensquared energy, and/or flux contrast
One or more of these performance metrics should be specified as a function of both science field
of view and of sky coverage (as a percentage)
3.1.6
Strehl, encircled energy, and/or point spread function stability
On both short and long time scales.
3.1.7 Differential astrometric precision
3.1.8 Throughput
Include specification for optical transmission in all science and wavefront sensor optical paths.
3.1.9 Emissivity
3.1.10 Operational efficiency
Include specifications on acquisition time and calibration time
3.2 Physical Characteristics
This section should describe any physical requirements or constraints on the product:
dimensional or weight limitations, acceptable or unacceptable materials, maximum power usage,
transportation and storage requirements, etc.
3.2.1 Mass
3.2.2 Space
3.2.3 Power consumption
3.2.4 Cooling requirements
3.3 Reliability
This section should describe the required availability of the system (e.g. allowable downtime for
maintenance), mean time between failures (MTBF) of key components, system performance
degradation in cases of component failure, etc.
3.4 Maintainability
This section should describe the allowable mean time to repair (MTTR), qualitative requirements
for accessibility, modular construction, test points, etc.
3.4.1 Test points
Indicate necessary diagnostic or calibration features with emphasis on operations, maintenance,
and integration and test.
Example: The MCAO system shall include a synthetic sodium asterism for internal calibration
and testing purposes.
Example: The ExAO system shall provide a means for automatically evaluating the health of
every deformable mirror actuator.
3.4.2 Maintenance personnel requirements
This section should estimate the required skills and workforce foreseen for preventive and other
maintenance (at the level sufficient for Systems Engineering planning).
Example: The ExAO system shall require daily cleaning of seven optical surfaces during ExAO
observations. This is estimated to require 2 hours of optical technician time per day.
3.5 Environmental Conditions
This section should describe the environments the equipment is expected to experience during
use, in storage, in service, and during shipment.
3.5.1 Natural Environment
Specifications should include Cn2 profile, sodium abundance, climate, seismic environment,
humidity, atmospheric pressure, etc.
3.5.2 Induced Environment
Specifications should include shock, mechanical vibration, acoustic noise, electromagnetic
interference, etc. that the product must accept.
Specification should also be made to indicate the environment the product is allowed to generate;
heat dissipation, mechanical vibration, etc.
3.6 Shipping requirements
This section should specify requirements specific to shipment to the summit.
Example: All items shall be transportable by commercial carrier without degradation in
performance. All containers shall be movable by forklift. All items over 50 kg which must be
moved at the Observatory shall have appropriate lifting eyes and mechanical strength to be lifted
by crane.
3.7 Design and Construction
This section should state minimum or essential requirements that are not specified by
performance characteristics or within related Interface Control Documents (ICDs). This can
include design standards, requirements on interchangeability, safety. This document should
concentrate on high-level issues that may affect architectural decisions. Detailed design
specifications will be made in the Design Requirements Documents (DRDs).
3.8 Facilities Requirements
This section should state the key requirements that might, early in the Observatory requirements
definition, be relevant to the Systems Engineering Group in consideration of Observatory-wide
issues.
3.8.1 Handling Tools
This should include requirements and limitations on the moving of the system
3.8.2 Lab Requirements