Common PDR ProblemsCommon PDR Problems

ACES Presentation

T. Gregory Guzik

March 6, 2003

Summary of Major Short FallsSummary of Major Short Falls 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 ObjectivesSection 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?– 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 DesignSection 4.0 Payload DesignPrinciple 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 SystemsSection 4.0 Systems Individual parts are not systems “Spacecraft” has five major systems

– Lift; Recovery; Payload; Beacon; Ground– Each of these has subsystems– Each subsystem has parts

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

The remainder of Section 4.0 details each of these systems, their subsystems and parts

Section 4.0 PowerSection 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 OtherSection 4.0 Other

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

Everyone had problems with thermal– Talk on Thermal issues on 3/13

Mechanical design was not developed– Related to thermal– Talk on Mechanical issues 3/13

The Development PhaseThe Development Phase

Detailed in-depth study including– 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

From 1/21 Project OverviewFrom 1/21 Project Overview

Critical Design Review (CDR)Critical Design Review (CDR)

Organized by the ACES ProgramResults from your development phaseDetermines whether you are ready to begin

building your payloadInclude written report and oral presentationPrecise date should be identified during

PDR

From 1/21 Project OverviewFrom 1/21 Project Overview

Section 6.0 ConstructionSection 6.0 Construction Software

– How will you get data OUT of storage?– How do you verify that your software works?

Testing– Listing the environment characteristics is NOT testing– Testing is quantitatively verifying that your

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 & AnalysisData Acquisition & Analysis What is your data rate, format & volume? What is a Data Analysis Plan?

– 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 & ScheduleManagement & ScheduleWhat 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

How do you develop a WBS and use it to establish a realistic schedule?– Review B. Ellison’s presentation

The WBS should be specificThe 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 pathWBS should not be presented down to more

than 2nd or 3rd levelUse one level more than presented to

estimate effort for task

Timeline follows the WBSTimeline follows the WBS Assign personnel to each task

– Tasks by different people can be done in parallel– Tasks by same person must be sequential

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) 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

BudgetsBudgets

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 IWGSpeaking of the IWG Not one project mentioned the IWG in their

management There are potentially many components across the

payloads that could be common – 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