Transcript Common PDR Problems

Common PDR Problems
ACES Presentation
T. Gregory Guzik
March 6, 2003
Summary of Major Short Falls
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No plots or tables showing expected results
Individual parts are not systems
How do you select an appropriate sensor / ADC?
No attempts to compute power requirements
How to compute thermal requirements?
Poor understanding of Development phase
How to get data OUT of on-board storage?
How do you test your payload?
What is the WBS & how do you use it?
Section 3.0 Mission Objectives
 What is the difference between mission, science and
technical goals?
– Mission is everything from launch to results
– Science is inquiry into nature
– Technical includes the practical aspects
 What are your expected results?
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From theory or previous measurements
Provides basis for instrument design
What sources are you measuring?
Needed for comparison with your data
 Generate Science Requirements
– What needs to be measured with what accuracy and frequency
Section 4.0 Payload Design
Principle of Operation
– Show how your payload design will function to
deliver the science requirements
– How do your sensors work?
– What is the expected accuracy of your
measurements?
– How will you cover the required range?
A “Traceability Matrix” shows the logical
flow from requirements to hardware
Section 4.0 Systems
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Individual parts are not systems
 “Spacecraft” has five major systems
– Lift; Recovery; Payload; Beacon; Ground
– Each of these has subsystems
– Each subsystem has parts
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What are the systems in your payload?
– Mechanical; Thermal; Power; Controller; Data
Acquisition; Data Archive; Sensors; Ground
– Each system has an interface to the other systems
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The remainder of Section 4.0 details each of these
systems, their subsystems and parts
Section 4.0 Power
 All had difficulty figuring out what to do about
power
– The power budget is a list of the voltage, current and
power (volts x current) required for all systems /
subsystems
– Obtain from specifications or measurements
– You then show how your power system will provide the
required voltage, currents and power for the mission
required time
 Need to take into account loss due to temperature
and voltage conversion
 More detailed talk on this subject on 3/11/03
Section 4.0 Other
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Everyone had difficulty figuring out how to pick
an appropriate sensor / ADC
– How do you condition the sensor for the ADC?
– Talk on Data Acquisition on 3/11
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Everyone had problems with thermal
– Talk on Thermal issues on 3/13
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Mechanical design was not developed
– Related to thermal
– Talk on Mechanical issues 3/13
The Development Phase
From 1/21 Project Overview
Detailed in-depth study including
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Test hardware concepts by prototyping
Finalize designs
Purchase long lead items (identified at PDR)
Establish interface controls
Complete fabrication plan
Finish integration & test plans
Complete operations & data analysis plans
Critical Design Review (CDR)
From 1/21 Project Overview
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Organized by the ACES Program
 Results from your development phase
 Determines whether you are ready to begin
building your payload
 Include written report and oral presentation
 Precise date should be identified during
PDR
Section 6.0 Construction
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Software
– How will you get data OUT of storage?
– How do you verify that your software works?
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Testing
– Listing the environment characteristics is NOT testing
– Testing is quantitatively verifying that your
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subsystems work
integrated payload works
payload will operate correctly under flight conditions
Calibrations
– What needs to be calibrated?
– How will you do the calibration?
– What do you do with the calibration data?
Data Acquisition & Analysis
 What is your data rate, format & volume?
 What is a Data Analysis Plan?
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All steps & components necessary to get results
How do you get data off your payload?
What is the analysis platform?
What processing are you going to do?
 “busting” data from your format
 applying calibrations
 correlating with other datasets
– What data products will you produce?
– What software will you use?
– What software needs to be developed?
Management & Schedule
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What is Interface Control?
– Listing your interfaces is in System Design
– Defining your interfaces is in detailed design
– How do you assure that ALL parties know
about, agree to & will build subsystems with
the correct interface
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How do you develop a WBS and use it to
establish a realistic schedule?
– Review B. Ellison’s presentation
The WBS should be specific
Include only the tasks you are actually
going to do
– Changing a few words in a sample WBS is
going to lead you down the wrong path
WBS should not be presented down to more
than 2nd or 3rd level
Use one level more than presented to
estimate effort for task
Timeline follows the WBS
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Assign personnel to each task
– Tasks by different people can be done in parallel
– Tasks by same person must be sequential
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What is the task dependency?
– What tasks must be completed prior to the start of a task (e.g.
Can’t integrate payload unless all subsystems are done)
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Need to distinguish between work time and calendar
time
 Would be wise to include contingency
 Identify milestones or major accomplishments
 Link tasks together with a Gantt chart
Budgets
 Long lead items where not always / clearly
identified
– Delivery requires more than 3 weeks
– Need to get requisition forms with three quotes in
ASAP
 All payloads probably have many common
components
– IWG should identify, specify and writeup requisition
forms
Speaking of the IWG
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Not one project mentioned the IWG in their
management
 There are potentially many components across the
payloads that could be common
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Develop solution only once
Common ADC, RTC and/or Memory chips
Common Data Format
Common Data Retrieval software
Common Data Processing software
Common parts pools (e.g. resistor, capacitor kits)
IWG should meet regularly to address such issues