1. Large Synoptic Survey Telescope (LSST)
  2. Observatory Control System
  3. Requirements
  4. German Schumacher and Francisco Delgado
  5. LSE-62
  6. Latest Revision Date: February 1, 2016
  7. Change Record
    1. Table of Contents
  8. The LSST Observatory Control System Requirements
    1. Introduction
    2. Document Scope
    3. Supporting Documents
    4. Definitions of Terms
    5. Verb Usage
  9. The LSST Observatory Control System Requirements
    1. 1 OCS Functional Requirements
      1. 1.1 Perform Observations
      2. 1.2 Perform Survey
      3. 1.3 Operational Requirements
      4. 1.4 Observatory Services
    2. 2 OCS Maintenance Requirements
      1. 2.1 Analysis
      2. 2.2 Maintenance Log
      3. 2.3 Maintenance Planning
      4. 2.4 System Maintenance
    3. 3 OCS Performance Requirements
      1. 3.1 OCS Unscheduled Downtime
      2. 3.2 Null Overhead
      3. 3.3 Communications Performance

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Large Synoptic Survey Telescope (LSST)

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Observatory Control System

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Requirements

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German Schumacher and Francisco Delgado

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LSE-62

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Latest Revision Date: February 1, 2016
This LSST document has been approved as a Content-Controlled Document. Its contents are subject to
configuration control and may not be changed, altered, or their provisions waived without prior
approval. If this document is changed or superseded, the new document will retain the Handle
designation shown above. The control is on the most recent digital document with this Handle in the
LSST digital archive and not printed versions.

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Change Record
Version
Date
Description
Owner name
1
5/31/2011
Initial Version
German Schumacher
and Francisco Delgado
2
6/14/2011
General Edits
F. Delgado
3
6/24/2011
General Edits
F. Delgado
4
2/1/2016
Incorporation of LCR-188 (addition of DMS-REQ-
0318 Data Management Unscheduled Downtime).
G. Schumacher and B.
Selvy

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ii
Table of Contents
Change
Record
...............................................................................................................................................
i
Introduction
.................................................................................................................................................
iii
Document
Scope
..........................................................................................................................................
iii
Supporting
Documents
................................................................................................................................
iii
Definitions
of
Terms
.....................................................................................................................................
iii
Verb
Usage
...................................................................................................................................................
iv
1
OCS Functional Requirements
................................................................................................. 1
1.1
Perform Observations
......................................................................................................... 1
1.2
Perform Survey
..................................................................................................................... 2
1.3
Operational Requirements
................................................................................................. 7
1.4
Observatory Services
........................................................................................................ 11
2
OCS Maintenance Requirements
........................................................................................... 13
2.1
Analysis
................................................................................................................................
13
2.2
Maintenance Log
................................................................................................................ 13
2.3
Maintenance Planning
...................................................................................................... 13
2.4
System Maintenance
......................................................................................................... 14
3
OCS Performance Requirements
........................................................................................... 14
3.1
OCS Unscheduled Downtime
.......................................................................................... 14
3.2
Null Overhead
..................................................................................................................... 14
3.3
Communications Performance
....................................................................................... 15

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The LSST Observatory Control System Requirements
Introduction
The Observatory Control System (OCS) is the master control system that schedules, commands,
coordinates, and monitors the observatory. The OCS is responsible for high level observatory operations
including user interfaces, sequencing, resource allocation and system monitoring and maintenance. The
OCS orchestrates and controls all aspects of the observatory for all observations (science, calibration,
and engineering) and all operation modes. The OCS coordinates the camera, telescope and data
management subsystems for an integrated operation during the survey. Through the OCS the system
can be started, monitored, adjusted during operations and stopped, both locally and remotely. The OCS
provides the means to support safe observatory operations during day and night.
The scheduling function of the OCS, considered the key component of this application, has as its main
function the ability to handle demands from several competing science programs, with different
requirements on cadence and sky location observations.
Document Scope
The OCS Requirements document describes high-level specific requirements for the observation
operational support to be implemented by the Observatory Control System, and it is derived from the
Observatory System Specifications document (TBD) and from the Operations Simulator survey baseline
document.
Supporting Documents
LSST Science Requirements Document (document LPM-17)
LSST System Requirements (document LSE-29)
LSST Observatory System Specifications (document LSE-30)
LSST Document Tree (document LSE-39)
Definitions of Terms
In this document a
requirement
refers to a declaration of a specified function or quantitative
performance that the delivered system or subsystem must meet. It is a statement that identifies a
necessary attribute, capability, characteristic, or quality of a system in order for the delivered system or
subsystem to meet a derived or higher requirement, constraint, or function.
This document uses the term
specification(s)
to mean one or more performance parameter(s) being
established by a requirement that the delivered system or subsystem must meet.
An
attribute
specifies a quantitative performance
parameter
in the context of the SysML based SysArch

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model used to generate this document.
A
constraint
is used to refer to an external limitation imposed on a delivered item under which it must
meet its requirements (e.g., the survey performance must be met under the constraint of the historical
weather pattern of the chosen site). A constraint in not a characteristic the system or subsystem itself
possesses.
Verb Usage
Statements of need, requirements, and constraints are written using one of three verbs that have a
specific meaning with respect to verification. All statements in this specification that convey operational,
functional, or performance needs, requirements, constraints, or goals on the LSST system will contain
one of these three verbs.
Will
A statement of fact. Will statements document something that will occur through the course
of normal design practice, project process, etc. These statements do not get formally verified.
Should
A goal. Should statements document a stretch goal. A should statement is typically
partnered with a shall statement. Should statements do not get formally verified.
Shall -
A requirement that gets formally verified. Shall statements document critical requirements
that must be verified through inspection, demonstration, analysis, or test during the verification
phase of the project to ensure objectively that the as-built design meets the requirement.

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The LSST Observatory Control System Requirements
1 OCS Functional Requirements
ID: OCS-REQ-0001
Last Modified: 2/2/2015
Specification:
The functional requirements comprise the operations and behavior that the OCS
implements to accomplish the data collection capabilities of the observatory.
Discussion
: The OCS works as the overall master control for the data collection functions of the
observatory. The data collection capabilities comprises the capture of science data from the Camera, as
well as, the acquisition of calibration and telemetry data system wide, needed to analyze the system
performance.
1.1 Perform Observations
ID: OCS-REQ-0002
Last Modified: 6/24/2011
Specification
: The OCS shall orchestrate the complete set of subsystems in the observatory to perform
observations.
Discussion
: An Observation is the sequence of telescope and camera setup operations, the exposure for
a certain time and the corresponding data delivery. These observations can be originated by a manual
request, or by an automatic mechanism.
The OCS coordinates the subsystems in all the phases of an observation, such as configuration, slew,
exposure, readout and storage of the image frames and the metadata. The Observing Modes are to be
selectable by an operator.
1.1.1
Science Observation
ID: OCS-REQ-0003
Last Modified: 6/23/2011
Specification
: The OCS shall orchestrate the execution and acquisition of science data from the
observatory.
Discussion
: The prime role of the OCS is to efficiently orchestrate the acquisition of the science images
and telemetry data from the observatory at all times of the day and night.
1.1.2
Calibration Observation
ID: OCS-REQ-0004
Last Modified: 6/23/2011
Specification
: The OCS shall orchestrate the acquisition of calibration data from the observatory.

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Discussion
: For acquiring calibration data, the OCS coordinates additional hardware that is not normally
utilized for regular science observations.
1.1.3
Engineering Observation
ID: OCS-REQ-0005
Last Modified: 11/30/2010
Specification
: The OCS shall orchestrate the execution and acquisition of engineering data from the
observatory.
Discussion
: This data is associated to the maintenance plan developed for the observatory.
1.2 Perform Survey
ID: OCS-REQ-0006
Last Modified: 6/23/2011
Specification
: The OCS shall control all the subsystems to conduct a survey over
Asky
area of sky; with
a median depth of
Nv1Sum
, using
FC
filters during a life time of
surveyTime
.
Discussion
: The parameter
Asky
is defined in LSR-REQ-0098 as 18000 SquareDegrees.
The parameter
Nv1Sum
is defined in LSR-REQ-0098 as 825 visits.
The parameter
FC
is defined in LSR-REQ-0082 as ugrizy.
The parameter
surveyTime
is derived from OSS-REQ--0097 as 10 years.
The cadence of visits and filter usage distribution is determined by the science programs demands
handled by the scheduler component of the OCS. Final priorities are set by an survey overseers
committee.
Description
Value
Unit
Name
The total area of sky covered by the median number of visits
shall be no less than
18000 SquareDeg
rees
Asky
The median number of visits for each place of the sky within
the main survey area shall be at least
825
Visit
Nv1Sum
The ugrizy filter set is based on the filters from the SDSS with
the addition of the y-band, These provide roughly uniform
sampling of the optical spectrum from 320-1000nm.
ugrizy
FC
Survey operations
10
Years
SurveyTime
1.2.1
Schedule Survey
ID: OCS-REQ-0007
Last Modified: 6/23/2011
Specification
: The OCS shall contain an automatic scheduler, which organizes the outstanding
observations in a way that optimizes observing time and achievement of the specified science goals.
Discussion
: The science goals are described in terms of science programs. The OCS Scheduler
includes these science programs as software components, with a high level of flexibility in order to be

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capable of implement the particular cadence and distribution of each one of them. Scripting capabilities
and adaptive parameters are also considered to cope with special purpose observations in the survey,
and potential changes of the survey baseline definition.
1.2.1.1
Fully automatic scheduling
ID: OCS-REQ-0008
Last Modified: 6/22/2011
Specification
: The OCS shall be capable of schedule and operate the sequence of observations in a fully
automated fashion during an entire night.
Discussion
: The OCS obtains all the relevant information from the science programs priorities, history of
observations, environmental conditions/forecasts and subsystems states in order to build the schedule
and conduct the survey automatically.
Obtain candidate observations automatically
ID: OCS-REQ-0009
Last Modified: 6/22/2011
Specification
: The OCS Scheduler shall generate the list of candidate target observations for a visit in a
fully automated fashion.
Discussion
: The science programs running in the OCS Scheduler will provide each one with its own list
of targets that are allowed to be observed and are also in need of visits. This group of lists is merged by
the scheduler to produce a single list of candidate targets for the next visit.
Rank candidates
ID: OCS-REQ-0010
Last Modified: 6/24/2011
Specification
: The OCS Scheduler shall evaluate the list of possible candidate targets with a numerical
rank, based on the history of observations and goals of the active science programs, in order to consider
the benefit of all the options in the scheduling algorithm.
Discussion
: Each science program contributes with its own list of ranked targets according to the
parameters for depth, filters, time interval distribution and specific cadence requirements. The scheduler
then takes these ranks into account when assembling the single ranked list of targets according to their
scientific priority for the next visit.
1.2.1.2
Schedule Science Programs
ID: OCS-REQ-0016
Last Modified: 6/22/2011
Specification
: The OCS Scheduler shall propose target observations according to the goals and
parameters of the science programs described in the Observatory System Specifications.

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Discussion
: The OCS Scheduler shall select the best observation target sequence from the list of
possible candidates, considering the benefit for the active science programs and the time cost of following
that particular sequence.
Keep track of each science program progress
ID: OCS-REQ-0017
Last Modified: 6/22/2011
Specification
: The OCS Scheduler shall keep track of the detailed progress of each science program.
Discussion
: In order to rank a particular sky field for the next visit, each science program needs to
consider the number of visits granted for that field, the sequence of filters and the time distribution
achieved so far, and evaluate those parameters for computing the science value for that particular field in
the next visit opportunity.
Observations Database
ID: OCS-REQ-0018
Last Modified: 6/23/2011
Specification
: The OCS shall keep a detailed observations database with the complete history of
observations with their parameters and environmental conditions under which they were taken.
Discussion
: This observations database is utilized for ranking the future visits and also for building
automatic and on-demand reports about the survey progress, globally and for each science program.
1.2.1.3
Optimize observing time
ID: OCS-REQ-0011
Last Modified: 6/24/2011
Specification
: The OCS Scheduler shall organize the sequence of observations optimizing the time
spent collecting data.
Discussion
: The natural way of achieving optimum observing time is by minimizing time spent slewing
and changing filters. This objective will sometimes go in the opposite interest of the science goals for
some science programs, and it is the job of the OCS scheduler to make the best balance between the two
for the time span of the survey.
Maximize science programs
ID: OCS-REQ-0012
Last Modified: 6/22/2011
Specification
: The OCS Scheduler shall pursue the maximum goals achievement for each science
program.

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Discussion
: The OCS Scheduler balances the attention given to each science program in order to obtain
scientific profit of each visit, trying also to find targets that satisfy multiple science programs
simultaneously.
Minimize slew time
ID: OCS-REQ-0013
Last Modified: 6/22/2011
Specification
: The OCS Scheduler shall minimize the time spent in slewing and maximize the shutter
open time.
Discussion
: The OCS Scheduler considers the cost of observing the next visit. The cost is the time
needed from the end of the current visit to reconfigure the observatory for starting the next visit. This is
the time to be spent slewing the telescope, slewing the dome, changing the filter and preparing the
camera for the exposures. The accumulation of these times during the night are to be minimized by
improving the rank of targets with shorter slews.
Estimate slew delay for candidate observations
ID: OCS-REQ-0014
Last Modified: 6/22/2011
Specification
: The OCS Scheduler shall estimate the slew delay time from the current state of the
observatory to the position of each possible next target, in order to consider the cost of all the options in
the scheduling algorithm.
Discussion
: The slew delay is evaluated for each target in the aggregated list of candidates, and this
time is considered along with the scientific rank in order to build the final ranked list of candidate targets
for automatically choosing the next visit.
1.2.1.4
Dynamic adaptation to changing conditions
ID: OCS-REQ-0015
Last Modified: 6/29/2011
Specification
: The OCS Scheduler shall constantly adapt the sequence of observations in real time,
according to the external environmental conditions and the particular requirements of sky quality of the
outstanding observations in the active science programs.
Discussion
: This short term adaptation must be in balance with the long term goals for the survey.
Telemetry from the environment is key for this requirement. Weather conditions are accounted for in the
ranking process of the targets.
1.2.1.5
Update Survey Parameters
ID: OCS-REQ-0020
Last Modified: 6/23/2011

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Specification
: The OCS provides the interface to allow the updating of the scheduler parameters
following the analysis of the survey progress by the survey managers.
Discussion
: The OCS Scheduler shall have a set of parameters that control the survey operation, such
as active science programs, relative priorities, ranking factors, time limits, sky brightness ranges, etc.
These parameters can be adjusted by the survey scientists and engineers after analyzing the survey
progress reports.
1.2.1.6
Schedule Calibration and Maintenance programs
ID: OCS-REQ-0019
Last Modified: 6/23/2011
Specification
: The OCS shall schedule calibration and maintenance programs, according to the baseline
plans. These programs shall allow automatic, scripted or manual observations according to the specific
operational needs.
Discussion
: During calibration and maintenance the OCS Scheduler works in a similar fashion, replacing
the science programs by calibration or maintenance programs.
1.2.1.7
Image Processing Control
ID: OCS-REQ-0021
Last Modified: 6/22/2011
Specification:
The OCS shall inform the Data Management System in advance of the image acquisition
of the needed processing related the specific image type.
Discussion:
This requirement ensures that the Data Management operating at the Base Facility has
advance notice of the type of image(s) that are being acquired. This is to inform the Data Management
system of the type of processing it needs to perform on the images as they are obtained.
1.2.2
Survey Lifetime
ID: OCS-REQ-0022
Last Modified: 6/24/2011
Specification
: The OCS shall support the observatory operations for the length of the 10 years survey
(
surveyTime
).
1.2.3
Survey Time Allocation
ID: OCS-REQ-0023
Last Modified: 6/14/2011
Specification
: The OCS scheduler shall provide the necessary capabilities and interfaces to allow the
execution of discretional observations different from the baseline survey.
1.2.4
Survey Monitor

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ID: OCS-REQ-0024
Last Modified: 11/29/2010
Specification
: The OCS shall constantly monitor the survey, computing metrics of the progress of each
science program.
Discussion
: Reports must be automatically generated, tables and plots. The progress will be measured
in terms of scheduled observations and similar metrics.
1.2.5
Survey Verification
ID: OCS-REQ-0060
Last Modified: 6/24/2011
Specification
: The OCS shall support the commissioning phase of the construction, and the science
verification phase prior to the survey.
1.3 Operational Requirements
ID: OCS-REQ-0025
Last Modified: 11/29/2010
Specification
: The OCS shall support different behaviors to accommodate several operating scenarios
depending on survey specifications and present conditions.
1.3.1
Operation Control
ID: OCS-REQ-0026
Last Modified: 11/29/2010
Specification
: The OCS shall be capable of commanding each subsystem of the data collection process
of the observatory, to perform the requested observations or operational procedures.
1.3.1.1
Hierarchical Control
ID: OCS-REQ-0027
Last Modified: 6/23/2011
Specification
: The OCS shall be capable of commanding the subsystems in a hierarchical way. Each
subsystem, Telescope Control System (TCS), Camera Control System (CCS) and Data Management
System (DMS) must have a command interface for OCS, and provide its status in a detailed level.
Discussion
: See the ICD documents LSE-70, LSE-74, LSE-71, LSE-72 and LSE-73 for a detailed
description of commands and status exchanges.
1.3.2
Observing Mode
ID: OCS-REQ-0028
Last Modified: 6/23/2011

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Specification
: The OCS supports different modes of observations, according to the established
observing plans.
1.3.2.1
Automatic Observation
ID: OCS-REQ-0029
Last Modified: 6/14/2011
Specification
: The OCS shall provide the means to perform observations in an automated fashion. It
shall coordinate all the devices of the subsystems involved in an observation or sequence of observations
in a reliable, safe and efficient way.
1.3.2.2
Manual Observation
ID: OCS-REQ-0030
Last Modified: 6/13/2011
Specification
: The OCS shall provide the means to perform manual observations, requested by an
operator. It must coordinate the devices in the subsystems according to the manual instructions given by
the user in the interfaces to perform the requested observation or sequence of observations.
1.3.2.3
Scripted Observation
ID: OCS-REQ-0031
Last Modified: 11/17/2010
Specification:
The OCS shall support sequencing of observations through user specified scripting of the
sequence.
Discussion:
This requirements supports the needs anticipated during commissioning, establishing
calibration sequences, and engineering and maintenance operations.
1.3.3
Control Mode
ID: OCS-REQ-0039
Last Modified: 3/2/2015
Specification
: The OCS shall be capable of being operated in a local and global configuration.
1.3.3.1
Global Control
ID: OCS-REQ-0062
Last Modified: 3/2/2015
Specification
: The OCS shall determine which system component has overall control of the data
acquisition within the observatory.
Discussion:
The OCS shall maintain a control token (a.k.a. "
the con
") which can, at the operator's
discretion, be passed to other components for controlling the data acquisition functions of the
observatory. The operator shall maintain an over-ride capability to take back "
the con
" as required.
The principle, here, is that there is a blurring between local and remote users. Users who wish to control
the data taking must first have enhanced privileges (somehow be known as "expert users") and

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specifically request "
the con
" from the operator. It will then be a human decision as to whether or not "
the
con
" is relinquished to the expert user. The software will then only operate from a singular control location
and other requests to control the data acquisition will be denied.
1.3.3.2
Local Control
ID: OCS-REQ-0063
Last Modified: 3/2/2015
Specification
: The OCS is considered in local control mode if the global control token is disabled.
Discussion:
The global control token (a.k.a "
the con
") is a binary flag: enabled or disabled. If enabled,
the system is in global control mode and the operator has "
the con
" unless s/he relinquishes it to an
expert user. If the global control token is disabled, then all the principal sub-systems are in local control
mode.
1.3.4
Operation Mode
ID: OCS-REQ-0032
Last Modified: 11/29/2010
Specification
: The OCS shall be capable of being operated from different locations.
1.3.4.1
Remote Operation
ID: OCS-REQ-0034
Last Modified: 6/23/2011
Specification
: The OCS shall provide the interfaces to operate the observatory from the designated
remote locations.
1.3.4.2
Summit Operation
ID: OCS-REQ-0033
Last Modified: 3/2/2015
Specification
: The OCS shall provide the interfaces to operate the observatory from the control room in
the summit.
1.3.5
User Interface
ID: OCS-REQ-0035
Last Modified: 6/13/2011
Specification
: The OCS shall provide interfaces for users to interact with its functionality.
Discussion
: Through the user interface, the system can be started, monitored, adjusted during
operations and stopped, both locally and remotely.
1.3.5.1
Access Control

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ID: OCS-REQ-0036
Last Modified: 11/29/2010
Specification
: The OCS shall control the access to the user interfaces with an authentication
mechanism.
1.3.5.2
Displays
ID: OCS-REQ-0037
Last Modified: 11/29/2010
Specification
: The OCS shall provide displays of system-wide state information.
1.3.5.3
GUI
ID: OCS-REQ-0038
Last Modified: 6/23/2011
Specification
: The OCS shall provide graphical and command line interfaces to facilitate the observatory
operations.
1.3.6
Change of subsystem state without failure
ID: OCS-REQ-0059
Last Modified: 6/23/2011
Specification
: The OCS shall not fail if a subsystem unexpectedly changes state, does not respond or
otherwise fails to operate as required.
Discussion
: The OCS will issue messages to the other subsystems to notify of this change of state or
failure in order to protect other subsystems from such a condition.
1.3.7
Graceful degradation
ID: OCS-REQ-0039
Last Modified: 6/23/2011
Specification
: The OCS shall enable the observatory to continue the survey in a gracefully degraded
mode in case of subsystems failures that still allow the acquisition of useful data.
Discussion
: When a device in a subsystem is in failure, the OCS disables that device and takes the
needed actions in the scheduling process in order to use the new limited range of observations that are
still useful for the science goals.
1.3.8
Safety
ID: OCS-REQ-0040
Last Modified: 6/24/2011
Specification
: The OCS shall follow the safety policies established by the Observatory System
Specifications (OSS-REQ-0098).

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Discussion
: The status of the safety system must be monitored by the OCS. Unsafe conditions must be
reported directly to the observatory operators as well as logged by the OCS. No part of the OCS is
allowed to be part of or interfere with, any observatory safety systems.
1.3.8.1
Interlock System
ID: OCS-REQ-0041
Last Modified: 6/22/2011
Specification
: The OCS shall follow the state of an external interlock system to abide for a safe operating
environment.
1.3.8.2
Safety Procedures
ID: OCS-REQ-0043
Last Modified: 6/22/2011
Specification
: The OCS shall enforce the application of safety procedures in the observatory operations.
1.4 Observatory Services
ID: OCS-REQ-0044
Last Modified: 6/23/2011
Specification
: The OCS provides services of common use observatory-wide, in order to optimize the use
of information technologies.
1.4.1
Configuration Database
ID: OCS-REQ-0045
Last Modified: 6/24/2011
Specification
: The Configuration Database shall manage the different configuration parameters needed
for each subsystem, for the different observing modes.
Discussion:
The Configuration Database maintains also the latest configuration utilized during
operations, that can be utilized for rapid restoration of service, in case of failure.
1.4.2
Engineering Facility Database
ID: OCS-REQ-0046
Last Modified: 6/22/2011
Specification
: The OCS shall capture, organize and store system-wide, time tagged state information to
make it available for monitoring, evaluation and calibration processes.
Discussion
: This section will implement the requirements on the functionality and performance of the
Engineering and Facility Database (EFD) as it relates to the Telescope, Camera, Data Management and
Calibration operations. This includes (but is not limited to) telemetry ingestion, replication of the EFD at

LSST Observatory Control System Requirements
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The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
12
Base and Archive sites, support of queries and instantiation of the EFD during the development phase of
the subsystems.
This telemetry and observatory condition information will be distributed to support both local and remote
operations in an efficient manner.
1.4.2.1
Availability of EFD contents
ID: OCS-REQ-0047
Last Modified: 6/23/2011
Specification
: All EFD contents shall be available for queries not impacting real time subsystems
activities.
Discussion
: A complex query like "raft 13 temperatures for past 2 years" may span EFD instances at
mountain, base, and archive and/or access centers. Such access must be user transparent. The
performance of a query processing is subject to a quality of service assignment.
1.4.2.2
Persistence of Telemetry
ID: OCS-REQ-0048
Last Modified: 6/24/2011
Specification
: The EFD shall persist all published observatory telemetry generated by the OCS,
telescope, camera and data management subsystems.
Discussion
: In particular, up to the defined limits in OSS -REQ-0311 and replicated here, all published
telemetry is captured reliably by the EFD, permanently.
Description
Value
Unit
Name
Long-term mean ingest rate to the Engineering and Facilities
Database required to be supported.
6.5
Mbit/sec
EFD_AvgRate
The minimum supported daily data volume of the engineering
facility data base.
30
GBytes
EFD_DayStore
Long-term mean ingest rate to the Engineering and Facilities
Database of non-science images required to be supported.
15.4
Mbit/sec
Blob_AvgRate
Maximum ingest rate to the Engineering and Facilities
Database of non-science images required to be supported.
21.9
Mbit/sec
NonScience_MaxRa
te
1.4.3
Middleware Communications
ID: OCS-REQ-0049
Last Modified: 6/22/2011
Specification
: The OCS shall implement a middleware communications layer to allow the commanding
and telemetry capture to all subsystems.
Discussion
: The baseline architecture of this middleware is based on the publish/subscribe protocol, as
defined by the Data Distribution Service (DDS) standard.The communications backbone runs on top of
the Observatory network infrastructure.

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1.4.4
System Monitor
ID: OCS-REQ-0050
Last Modified: 6/22/2011
Specification
: The OCS shall provide the means for a continuous system monitoring, during night time
as well as day time, giving support for the science, calibration and engineering observations, status and
activities, also facilitating the hand over of the system between users in different work shifts.
Discussion
: One of the important monitoring functions is a comprehensive handling of events
incorporated into the telemetry stream, logged as a component of the EFD.
2 OCS Maintenance Requirements
ID: OCS-REQ-0051
Last Modified: 2/2/2015
Specification
: The OCS shall support the maintenance activities of the observatory, capturing and
storing telemetry, coordinating routine maintenance operations and providing interfaces to the users to
evaluate and perform maintenance jobs.
2.1 Analysis
ID: OCS-REQ-0052
Last Modified: 6/23/2011
Specification
: The OCS shall provide tools for the analysis of telemetry and state information in order to
optimize the system and to measure performance trends over long periods.
Discussion
: The analysis tool set is intended to be flexible and expandable, to cope with specific
demands from the subsystems. The subsystems may develop extensions using the infrastructure
provided by the tool like EFD access and report and graphics generation.
2.2 Maintenance Log
ID: OCS-REQ-0053
Last Modified: 6/23/2011
Specification
: The OCS shall maintain a log of all the maintenance activities. The OCS shall provide an
interface to manually generate the complimentary maintenance information that it is not possible to obtain
through the telemetry. This interface shall also allow to obtain and analyze the information about the
maintenance activities performed in every subsystem.
2.3 Maintenance Planning
ID: OCS-REQ-0054
Last Modified: 6/23/2011
Specification
: The OCS shall support the planning of maintenance activities to perform preventive
maintenance in order to achieve the reliability goals of the system.

LSST Observatory Control System Requirements
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The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
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14
Discussion
: The outcome of the planning activities will be a report with the proposed job(s) to be
performed at the observatory.
2.4 System Maintenance
ID: OCS-REQ-0055
Last Modified: 6/23/2011
Specification
: The OCS shall provide the means for performing and supporting maintenance activities in
the observatory. The OCS shall provide the tools to support the scheduled maintenance jobs originated
as a result of the planning activities.
Discussion
: The support comprises the coordination of the subsystems in activities like, getting a new
pointing model set of parameters in the TCS with the computations from the DM.
3 OCS Performance Requirements
ID: OCS-REQ-0056
Last Modified: 2/2/2015
Specification
: The OCS contributes to the performance of the observatory, scheduling the survey with
the goal of maximize the specified science observations, and coordinating the subsystems efficiently in all
the automatic observation modes.
3.1 OCS Unscheduled Downtime
ID: OCS-REQ-0057
Last Modified: 1/27/2015
Specification:
The OCS subsystem shall be designed to facilitate unplanned repair activities expected
not to exceed a suballocation of
TSUnSchDowntime
days per year.
Discussion:
For the purpose of design and construction, unscheduled downtime requirements have
been allocated based on work packages where the OCS is a part of the Telescope and Site. This
principle is reflected in the negotiated T&S allocation found in LCR-188.
The T&S subsystem will work with the OCS to determine the appropriate OCS allocation from the
TSUnSchedDowntime allocation specified in TLS-REQ-0150.
This requirement does not invoke the need to verify by reliability analysis. Verification is by analysis that
identifies likely hardware failures and identifies mitigations to minimize downtime caused by those
failures.
3.2 Null Overhead
ID: OCS-REQ-0058
Last Modified: 6/23/2011

LSST Observatory Control System Requirements
LSE-62
Latest Revision 2/1/2016
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
15
Specification
: The OCS control and scheduling activities shall not add overhead time to the operation of
the observatory. The commanding and telemetry traffic delays shall be negligible in comparison to the
control time constants of the subsystems.
Discussion
: All the eventual time consuming OCS activities (such as scheduling computations) will be
performed in advance to the actual observations and in parallel to the already defined sequence of
activities.
3.3 Communications Performance
ID: OCS-REQ-0061
Last Modified: 6/24/2011
Specification
: The OCS middleware communications performance shall comply with a latency of less
than
ocsMsgLatency
, a throughput of at least
ocsMsgRate
, and a data persistence of at least
ocsMsgPersistence
.
Description
Value
Unit
Name
The message transmission in the OCS middleware has a
latency of less than
300e-6
Seconds
ocsMsgLatency
The OCS middleware has the capacity of handling messages
at a rate of at least
50e3
Hz
ocsMsgRate
The message persistence of a particular parameter in the
OCS middleware is of at least
2
messages
history
ocsMsgPersistence

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