# Presentation: 116784

## ICESat Flight Dynamics SystemPreliminary Design Review

**September 14, 1999**

## Agenda

**Introduction****	****	****	****	****	****	****9:00-9:15**
**Requirements Document/Compliance Matrix****	****	****9:15-9:20**
**Block Diagram****	****	****	****	****	****9:20-9:30**
**Requirements Review****	****	****	****	****	****9:30-11:00**
**Interfaces****	****	****	****	****	****	****11:00-11:30**
**Lunch****	****	****	****	****	****	****11:30-12:30**
**Trades/Testing/Staffing****	****	****	****	****12:30-1:00**
**Key Issues/Risk ****	****	****	****	****	****1:00-1:15**
**Concept of Operations****	****	****	****	****1:15-1:30**
**Schedule****	****	****	****	****	****	****1:30-1:40**
**Special Topics (orbit determination, off-nadir pointing)****	****1:40-2:15**
**Conclusions****	****	****	****	****	****	****2:15-2:30**

## Introduction

**Welcome**
**Ed and Rich **
**Review participants:**
**Ball      (s/c builder, system integration, MOC)**
**LASP      (s/c operations, MOC)**
**GSFC      (program office, MMFD)**
**UT      (science team)**
**Others      (Raytheon (s/w), ??)**

## Objectives and Characteristics of the FDS

**Objective of the ICESat Flight Dynamics System (FDS) is to provide all navigation functions for the mission*, including:**
**Estimate and predict the observatory orbit to enable communication antenna pointing**
**Estimate and predict the observatory orbit to monitor groundtrack location to meet science objectives**
**Maintain the observatory in its required orbit to meet the science objectives**
**Calculate observatory pointing commands to maximize science yield**
*** Early orbit support from MMFD at GSFC **
** **
**Characteristics of the ICESat Flight Dynamics System:**
**Ground-based**
**Part of the Mission Operations Center (MOC)**
**Located at LASP, at the University of Colorado**
**Highly automated**
**Operated by a mix of LASP professionals and students, and Ball engineers**

## Objectives and Goals of this Review

**Review all Flight Dynamics requirements, interfaces, documentation, risks, concept of operations, etc.**
**Describe the current FDS design and concepts to experts and other interested parties (ICESat Program Office, ICESat Science Team, MMFD) for discussion and critique**
**Establish that the system design meets the requirements**
**Identify any incomplete or inadequate areas in the current FDS design**
**Concentrate on review of the system requirements, and how each will be satisfied**

## Themes for the ICESat Flight Dynamics System

** **
** **
**	****FDS design complies with all requirements**
** **
** **
** **
**	****Reuse of QuikScat and GFO**

## Requirements are Well-Defined and Documented

**“****ICESat Flight Dynamics Detailed Requirements and Specification” **
**Draft available for comments/critiques**
**Will eventually be part of MOC documentation**
**Restatement of the Flight Dynamics section of the MOC RFP, made to read like a spec:**
**Added appropriate shalls and wills**
**One requirement per paragraph**
** **
** **
**Compliance matrix**
**Next 7 slides**
**Verification methods:**
**	****I = inspection - examination or measurement**
**	****A = analysis - theoretical or empirical analyses**
**	****T = test - measurement of performance parameters **
**	****D = demonstration - actual conduct or use**

## Compliance Matrix (1 of 7)

**Section****	****	****Requirement****	****	****	****Verification Method****	**
**3.1****	****	****NASA Provided Flight Dynamics Services****	****	****	****D****	**
**3.2****	****	****Mission Characteristics****	****	****	****	****D****	**
**3.2.1****	****Raw Data Latency****	****	****	****	****	****D****	**
**3.3****	****	****Software, Hardware, Personnel, and Facilities****	****	****-****	**
**3.3.1****	****Software and Hardware****	****	****	****	****I****	**
**3.3.2****	****Personnel and Facilities****	****	****	****	****I****	**
**3.4****	****	****Mission Phases Support****	****	****	****	****-****	**
**3.4.1****	****Maneuver Constraints****	****	****	****	****-****	**
**3.4.1.1****	****High Latitudes****	****	****	****	****	****I****	**
**3.4.1.2****	****Single maneuver****	****	****	****	****	****I****	**
**3.4.1.3****	****Frozen Orbit Maintenance****	****	****	****	****I****	**
**3.4.1.4****	****Maneuver Frequency****	****	****	****	****	****I****	**
**3.4.2****	****Pre-Launch Phase****	****	****	****	****	****-****	**
**3.4.2.1****	****Mission Analysis and Delta-V Budget****	****	****	****A **
**3.4.2.2****	****Injection Orbit Selection****	****	****	****	****A****	**
**3.4.2.3****	****Reentry Analysis****	****	****	****	****	****A****	**
**3.4.2.4****	****Ground Station Coverage****	****	****	****	****A****	**
**3.4.2.5****	****Launch Window****	****	****	****	****	****A**

## Compliance Matrix (2 of 7)

**Section****	****	****Requirement****	****	****	****Verification Method****	**
**3.4.2.6****	****Operations Planning****	****	****	****	****	****D****	**
**3.4.3****	****Checkout Phase****	****	****	****	****	****-****	**
**3.4.3.1****	****Separation Vector****	****	****	****	****	****D****	**
**3.4.3.2****	****Planning and Calibration – Orbit Raising****	****	****	****D****	**
**3.4.3.3****	****Planning and Calibration – Orbit Maintenance****	****	****D****	**
**3.4.3.4****	****Planning and Calibration - Inclination****	****	****	****D****	**
**3.4.3.5****	****Thruster Calibration – Orbit Attainment****	****	****	****D****	**
**3.4.3.6****	****Thruster Calibration – Orbit Maintenance****	****	****	****D****	**
**3.4.3.7****	****Orbit Determination and Prediction****	****	****	****D****	**
**3.4.3.8****	****On-board Attitude Verification****	****	****	****	****D****	**
**3.4.3.9****	****Anomaly Resolution****	****	****	****	****	****D****	**
**3.4.3.10****	****Sensor Calibration****	****	****	****	****	****D****	**
**3.4.3.11****	****Provide IIRVs****	****	****	****	****	****D****	**
**3.4.3.12****	****Convert Maneuver Plan****	****	****	****	****D****	**
**3.4.4****	****Calibration and Validation Phase****	****	****	****-****	**
**3.4.4.1****	****Planning and Calibration****	****	****	****	****D****	**
**3.4.4.2****	****On-board Orbit and Attitude Determination****	****	****	****D****	**
**3.4.4.3****	****Anomaly Resolution****	****	****	****	****	****D****	**

## Compliance Matrix (3 of 7)

**Section****	****	****Requirement****	****	****	****Verification Method****	**
**3.4.4.4****	****Sensor Calibration****	****	****	****	****	****D****	**
**3.4.4.5****	****Generation of Planning Data****	****	****	****	****D****	**
**3.4.4.6****	****Provide IIRVs****	****	****	****	****	****D****	**
**3.4.4.7****	****Convert Maneuver Plan****	****	****	****	****D****	**
**3.4.5****	****Maneuver Planning****	****	****	****	****	****D****	**
**3.4.5.1****	****Drag Make-up Maneuvers****	****	****	****	****D****	**
**3.4.5.2****	****Inclination Maneuvers****	****	****	****	****D****	**
**3.4.5.3****	****Orbit Change Maneuvers****	****	****	****	****D****	**
**3.4.6****	****Groundtrack Monitoring and Prediction****	****	****	****-****	**
**3.4.6.1****	****Groundtrack Monitoring****	****	****	****	****D****	**
**3.4.6.2****	****Groundtrack Prediction****	****	****	****	****D****	**
**3.4.6.3****	****Output****	****	****	****	****	****	****D****	**
**3.4.7****	****Mission Planning Support****	****	****	****	****-****	**
**3.4.7.1****	****Real-Time Attitude****	****	****	****	****	****D****	**
**3.4.7.2****	****Mission Planning****	****	****	****	****	****D****	**
**3.4.7.3****	****Attitude Sensor Monitoring****	****	****	****	****D****	**
**3.4.7.4****	****Predict Ephemeris and Maneuver Planning****	****	****	****D****	**
**3.4.7.5****	****Maneuver Monitoring****	****	****	****	****	****D****	**

## Compliance Matrix (4 of 7)

**Section****	****	****Requirement****	****	****	****Verification Method****	**
**3.4.7.6****	****Acquisition Data****	****	****	****	****	****D****	**
**3.4.7.7****	****Post-Maneuver State****	****	****	****	****	****D****	**
**3.5****	****	****Orbit & Attitude Determination****	****	****	****	****-****	**
**3.5.1****	****Operational Orbit Determination ****	****	****	****D****	**
**3.5.1.1****	****Operational Orbit Determination Accuracy****	****	****	****-****	**
**3.5.1.1.1****	****Along Track Position****	****	****	****	****	****A****	**
**3.5.1.1.2****	****Across Track Position****	****	****	****	****A****	**
**3.5.1.1.3****	****Radial Position****	****	****	****	****	****A****	**
**3.5.1.1.4****	****Solution Latency****	****	****	****	****	****D****	**
**3.5.1.1.5****	****Comparison with POD****	****	****	****	****D****	**
**3.5.1.2****	****Propagation Accuracy – Without Maneuver****	****	****	****-****	**
**3.5.1.2.1****	****Along Track Position****	****	****	****	****	****A****	**
**3.5.1.2.2****	****Across Track Position****	****	****	****	****A****	**
**3.5.1.2.3****	****Radial Position****	****	****	****	****	****A****	**
**3.5.1.2.4****	****Propagation Latency****	****	****	****	****	****D****	**
**3.5.1.3****	****Propagation Accuracy – With Maneuver****	****	****	****-****	**
**3.5.1.3.1****	****Along Track Position****	****	****	****	****	****A****	**
**3.5.1.3.2****	****Across Track Position****	****	****	****	****A****	**

## Compliance Matrix (5 of 7)

**Section****	****	****Requirement****	****	****	****Verification Method****	**
**3.5.1.3.3****	****Radial Position****	****	****	****	****	****A****	**
**3.5.1.3.4****	****Propagation Latency****	****	****	****	****	****D****	**
**3.5.2****	****Operational Attitude Support****	****	****	****	****-****	**
**3.5.2.1****	****Off-Nadir Pointing Monitoring****	****	****	****	****D****	**
**3.5.2.2****	****Off-Nadir Pointing Quaternion Generation****	****	****	****D****	**
**3.6****	****	****Sensor Support****	****	****	****	****	****D****	**
**3.6.1****	****Sensor Uploadable Parameters Support****	****	****	****-****	**
**3.6.1.1****	****Star Tracker****	****	****	****	****	****-****	**
**3.6.1.1.1****	****Proper Stellar Motion****	****	****	****	****	****D****	**
**3.6.1.1.2****	****Star Precession****	****	****	****	****	****D****	**
**3.6.1.2****	****GPS Initial Condition Vector****	****	****	****	****D****	**
**3.6.1.3****	****Magnetic Field****	****	****	****	****	****D****	**
**3.6.2****	****Sensor Calibration Support****	****	****	****	****-****	**
**3.6.2.1****	****Star Tracker and IRU****	****	****	****	****	****D****	**
**3.6.2.2****	****Star Tracker FOV****	****	****	****	****	****D****	**
**3.6.2.3****	****IRU Scale Factors and Rate Drift****	****	****	****	****D****	**
**3.7****	****	****Products Exchange****	****	****	****	****	****-****	**
**3.7.1****	****FDS Products to the Mission Operations Center****	****	****-****	**

## Compliance Matrix (6 of 7)

**Section****	****	****Requirement****	****	****	****Verification Method****	**
**3.7.1.1****	****Orbit Solutions****	****	****	****	****	****D****	**
**3.7.1.2****	****Maneuver Design****	****	****	****	****	****D****	**
**3.7.1.3****	****Groundtrack Offset****	****	****	****	****	****D****	**
**3.7.1.4****	****Frozen Orbit Parameters****	****	****	****	****D****	**
**3.7.1.5****	****Initial Condition Vector****	****	****	****	****D****	**
**3.7.1.6****	****Base Time Load****	****	****	****	****	****D****	**
**3.7.1.7****	****Orbit and Attitude Verification****	****	****	****	****D****	**
**3.7.2****	****MOC Products to the Flight Dynamics System****	****	****-****	**
**3.7.2.1****	****Propulsion Data****	****	****	****	****	****D****	**
**3.7.2.2****	****All S-Band Data****	****	****	****	****	****D****	**
**3.7.2.3****	****Solar Array Encoder Data****	****	****	****	****D****	**
**3.7.3****	****Flight Dynamics Products to the Science Team****	****	****-****	**
**3.7.3.1****	****Inertia and Mass Properties****	****	****	****	****D****	**
**3.7.3.2****	****Maneuver Plans****	****	****	****	****	****D****	**
**3.7.3.3****	****OOD Solutions****	****	****	****	****	****D****	**
**3.7.3.4****	****Star Tracker Data****	****	****	****	****	****D****	**
**3.7.4****	****Data and Products Archive****	****	****	****	****-****	**
**3.7.4.1****	****Permanent Archive****	****	****	****	****	****D****	**

## Compliance Matrix (7 of 7)

**Section****	****	****Requirement****	****	****	****Verification Method****	**
**3.7.4.2****	****Archive Accessibility****	****	****	****	****	****D****	**
**3.8****	****	****Reliability****	****	****	****	****	****	****-****	**
**3.8.1****	****Availability****	****	****	****	****	****	****A****	**
**3.8.2****	****Single Point Failures****	****	****	****	****	****I****	**
**3.8.3****	****Maintenance****	****	****	****	****	****D****	**
**3.9****	****	****Security****	****	****	****	****	****	****-****	**
**3.9.1****	****Physical Security****	****	****	****	****	****I****	**
**3.9.2****	****Computer Systems****	****	****	****	****	****I****	**
**3.9.3****	****Databases****	****	****	****	****	****	****I****	**
**3.9.4****	****Backups****	****	****	****	****	****	****I****	**
**3.10****	****Integration and Testing Support****	****	****	****	****D****	**
**3.11****	****Documentation****	****	****	****	****	****D****	**
**3.11.1****	****Interface Control Document****	****	****	****	****D****	**
**3.11.2****	****Specification****	****	****	****	****	****D****	**
**3.11.3****	****Test Plan****	****	****	****	****	****	****D****	**
**3.11.4****	****Operations Handbook****	****	****	****	****	****D****	**
**3.11.5****	****Operational Agreements****	****	****	****	****D****	**
**3.12****	****Reviews****	****	****	****	****	****	****-****	**
**3.12.1****	****PDR****	****	****	****	****	****	****D****	**
**3.12.2****	****CDR****	****	****	****	****	****	****D**

## Flight Dynamics Block Diagram

## Requirements Review - Intro

**Review each requirement in spec (as well as in RFP and proposal)**
** **
**Describe how each will be met**

## Requirements Review -Data from MMFD, ERO, Data Latency

## Requirements Review - S/W, H/W, Personnel, Facilities

## Requirements Review -Maneuver Constraints

## Requirements Review -Pre-Launch Phase

## Requirements Review -Checkout Phase (1 of 2)

## Requirements Review - Checkout Phase (2 of 2)

## Requirements Review - Calibration and Validation Phase

## Requirements Review - Maneuver Planning

## Requirements Review - Groundtrack Monitoring and Prediction

## Requirements Review - Mission Planning Support

## Requirements Review - Operational Orbit Determination (1)

## Requirements Review - Operational Orbit Determination (2)

## Requirements Review - Propagation without Maneuver

## Requirements Review - Propagation with Maneuver

## Requirements Review - Operational Attitude Support

## Requirements Review - Sensor Support

## Requirements Review - Sensor Calibration Support

## Requirements Review - FDS Products to the MOC

## Requirements Review - MOC Products to FDS

## Requirements Review - FDS Products to Science Team

## Requirements Review - Archive, Availability

## Requirements Review - Security

## Requirements Review - I&T Support, Documentation

## Flight Dynamics Block Diagram

## Interface Control Document

**“****ICESat Flight Dynamics System External Interface Control Document” **
**Draft available for comments/critiques**
**Will eventually be part of MOC documentation**
** **
**Flight Dynamics System has interfaces to:**
**MOC**
**MMFD (Multi-Mission Flight Dynamics at Goddard)**
**Tracking stations (EPGS, WOTIS)**
**JPL**
**Science Team**

## Interfaces to the MOC (1 of 3)

**Interfaces are simplified considerably because of co-location of the FDS with the MOC**
**MOC personnel will also run FDS**
**Real time operations performed by the MOC**
**MOC will perform off-line functions (planning and scheduling, orbit and attitude analysis, data archiving, and housekeeping telemetry data processing, checking, archiving, etc.)**
**Data transfer will be via the LASP computer network**
**Planning/Scheduling Products**
**FDS will generate; transfer to the MOC**
**Produced by STK s/w, predictions of: **
**Station contact times,apogee/perigee times, ascending node times, eclipse entry/exit times**
**ICVs**
**Base time load**
**Maneuver Plan**
**For all orbit change or maintenance maneuvers, FDS will provide thruster on and off times, and spacecraft attitude**

## Interfaces to the MOC (2 of 3)

**GPS Data**
**Tracking data from the flight receiver will be stripped from the downlink by the MOC**
**Data will be received, formatted, and archived by the MOC**
**Propulsion Data**
**Propellant tank pressure and temperature will be available from the MOC**
**Used by FDS for propulsion system modeling**
**Data will be received, formatted, and archived by the MOC**
**Groundtrack Monitoring**
**FDS will provide data (plots and tables) for groundtrack monitoring and prediction**
**Frozen Orbit Monitoring**
**FDS will provide data (plots and tables) of the frozen orbit parameters**
**Orbit and Attitude Verification**
**Support orbit and attitude verification**
**Solar Array Encoder Data**

## Interfaces to the MOC (3 of 3)

**Attitude Quaternions**
**FDS will provide pointing quaternions to the MOC**
**Small roll angle to point the laser at the ideal groundtrack**
**Calculated using software developed by CCAR, running on the LASP computer network**
**S-Band Data**
**All S-Band data will be available to FDS**
**MOC will receive, format, and archive these data**
**Operational Orbit Determination Solution**
**FDS will provide the OOD solution and propagations to the MOC**
**Archive**
**FDS data will be provided to the MOC for archiving**
**All important (TBD) data from the main FDS functions:**
**Planning and scheduling products from STK**
**OOD solutions from MicroCosm**
**Maneuver designs from maneuver planning s/w**
**Groundtrack monitoring and prediction data**
**Off-nadir pointing quaternion data**

## Interfaces to Multi Mission Flight Dynamics (1 of 2)

**Multi Mission Flight Dynamics (MMFD) will support pre-launch and early orbit operations**
**Support will nominally decrease gradually and terminate 3 weeks after launch**
**Data provided:**
**Tracking System Accuracy**
**MMFD will work with the NASA ground stations to analyze and verify tracking system accuracy**
**Post-Separation Trajectory Predictions**
**MMFD will interface with the launch vehicle contractor to acquire and process the launch and post-separation trajectory data**
**Launch Data**
**MMFD will interface with the launch site to acquire and process Launch Trajectory Ascent System (LTAS) data and Redundant Inertial Flight Control Assembly (RIFCA) data for the initial trajectory prediction**
**NORAD Data**
**MMFD will interface with NORAD to acquire and process NORAD tracking data for trajectory prediction**

## Interfaces to Multi Mission Flight Dynamics (2 of 2)

**Universal Tracking Data Format (UTDF) Data**
**MMFD will interface with the NASA ground stations to acquire and process UTDF angles tracking data and estimate the trajectory**
**Post Separation Trajectory**
**MMFD will generate an initial orbit prediction after s/c separation and distribute it as an IIRV to the DSN, MOC (FDS), and WOTIS **
**Update Orbit Predictions - First 24 Hours**
**MMFD will update initial orbit predictions as needed for the first 24 hours after launch with the first delivery between L+4 and L+6 hours. Each update will be distributed to the DSN, MOC (FDS), and WOTIS ****	**
**Update Orbit Predictions - First Week**
**MMFD will update initial orbit predictions every 24 hours for the first week after launch and distribute them to the DSN, MOC (FDS), and WOTIS**
**Orbit Determination**
**If GPS data is not available, MMFD will perform orbit determination based on angle data and distribute the solutions to the FDS**
**Maneuver Verification**
**MMFD will**** ****provide consultation for maneuver and trajectory planning**

## Interfaces to the Tracking Stations and JPL

**Interfaces to the Tracking Stations - IIRVs**
**FDS will provide Improved Inter-Range Vectors (IIRVs) to the tracking stations (EPGS through WOTIS)**
**Used to point the communication antennas**
**Standard IIRV format**
** **
**Interfaces to JPL - GPS Data**
**GPS tracking data from the IGS network of ground tracking sites will be obtained from JPL**
**Data processed with GPS data from the flight receiver to produce OOD solutions**
**Daily during routine ops, and by operator request during early orbit ops**
**Data obtained over the Internet or via ftp (through LASP firewall)**

## Interfaces to the Science Team(1 of 2)

**Science Team is distributed at various academic and government institutions around the country and world; directed from UT/CSR**
**Data transfer will be via the Internet or ftp, from project database/archive at the MOC**
**Operational Orbit Determination Solution**
**FDS will provide the OOD solution to the ST**
**Maneuver Plan**
**FDS will provide the maneuver plans to the ST**
**Thruster on and off times, delta-v, and s/c attitude**
**Precision Orbit Determination Solutions**
**ST will periodically provide POD solutions**
**Used to verify and evaluate the accuracy of the OOD solutions**
**Spacecraft Mass Properties**
**FDS will provide the ST s/c mass and inertia properties, including their variations**
**Data used for POD**

## Interfaces to the Science Team(1 of 2)

**Star Tracker Data**
**From the bus (CT-602) star tracker**
**Data from instrument star tracker to ST via ??**
**Targets of Opportunity for Off-Nadir Pointing**
**Information from the ST to the FDS**
**Format TBD**

## Flight Dynamics Trade Studies

** **
**Orbit determination software - done**
**Groundtrack monitoring and maneuver design software - done**
** **
**No future trades planned**

## Orbit Determination Software Trade

**Requirement: perform orbit determination to few-meter accuracy using GPS data**
** **
**Possible software packages:**
**MicroCosm (derivative of Goddard’s Geodyn)**
**Geodyn (Goddard)**
**Gipsy/Oasis II (JPL)**
**MSODP (UT)**
** **
**All are capable of meeting requirements**
** **
**MicroCosm is the obvious choice because:**
**MicroCosm installed at LASP and used for QuikScat**
**LASP has license**
**CCAR personnel have experience scripting, running, and optimizing MicroCosm**

## Groundtrack Monitoring and Maneuver Design Software Trade Study (1 of 2)

**Requirements: **
**Monitor groundtrack repeat at all latitudes**
**Design maneuvers to maintain orbit**
**Design maneuvers to change orbits**
** **
**Possible options:**
**Gtarg and Osmean system built by Ball**
**Software Gtarg and Osmean written by JPL for Topex**
**Scripts and interfaces to run system built by Ball for GFO**
**Used for first 6-8 months of mission**
**System built by Raytheon**
**Developed to be more automated than Gtarg system**
**Entire system built by Raytheon for GFO**
**Currently being used for GFO**

## Groundtrack Monitoring and Maneuver Design Software Trade Study (2 of 2)

**Package****	****Advantages****	****	****Disadvantages**
**Gtarg****	****	****I/F by Ball - insight****	****More operator intervention;**
**	****	****	****into FDS/MOC system****	****especially for changing orbit**
**Raytheon****	****More automated**
**	****	****	****Less expensive**
**Raytheon software system selected**
**Contract Implementation/Requirements Review meeting this Friday**

## Unit Testing Performed Independently for Each Component

**Testing of some components will be minimal**
**Because of their continued use on QuikScat**
**Such as: interface with EPGS, generate planning/scheduling products**
**Unit testing of components is the responsibility of the contractors**
**Orbit determination:**
**Process simulated data, compare to “truth”**
**Process Topex and GFO data, compare to NASA POD**
**Groundtrack monitoring and maneuver planning:**
**Test with simulated data, compare to “truth”**
**Test with GFO data, compare to GFO ops**
**Off-nadir pointing:**
**Test with simulated data, compare to “truth”**

## System Testing with End to End Test

**System end to end test scheduled for January 2001**
**Generate GPS data with SWTB**
**GPS simulator, GPS EMU receiver in loop**
**Strip data from X-band downlink (?)**
**Process GPS data with orbit determination software**
**Orbit determination solution to:**
**STK s/w - generate planning/scheduling products**
**Groundtrack monitoring s/w:**
**Generate groundtrack predictions, plots, tables**
**Plan maintenance maneuvers**
**Generate commands for maneuvers**
**Off-nadir pointing s/w:**
**Generate pointing quaternions**
**Generate pointing commands**
**Check all products to verify performance**

## Staffing - Key Personnel have a Wealth of Relevant Experience

**Michelle Kelley - LASP Mission Operations Manager**
**Experience includes 9 years of s/c ops, Deputy Mission Operations Manager for SNOE and QuikScat**
**Dan Kubitschek - CCAR Research Associate**
**Experience includes setting up, operating, and optimizing the QuikScat orbit determination system; principal for ICESat off-nadir pointing algorithm development and software**
**Chris Cox - Raytheon engineer**
**Experience includes writing groundtrack monitoring and maneuver design software for GFO and Landsat**
**Scott Mitchell - Ball FDS Coordinator**
**Experience includes GFO orbit attainment and maintenance, QuikScat orbit raising**
**Other high quality people available as needed:**
**LASP - Randy Davis, Sean Ryan, Alain Jouchoux **
**CCAR - George Born, Penny Axelrad, Kenn Gold**
**Ball - Ian Gravseth, Lisa Ward**
**Raytheon - Steve Klosko, Craig Johnson**

## Staffing - Planned Level of Effort by all Groups is Easily Attainable

**Number of Equivalent People (EPs) for FDS by calendar year:**
**	****	****	****---------------------- Calendar Year --------------------**
**Entity****	****	****99****	****00****	****01****	****02****	****03****	****04**
**Ball (FDS)****	****0.8****	****0.4****	****0.4****	****0.4****	****0.4 ****	****0.4**
**LASP (FDS)****	****1.0****	****1.1****	****1.1**
**(to L+30 days)**
**LASP (FOT) ****	****	****	****13.3****	****9.2****	****8.0         8.3****	**
**(includes FDS)**
**(from L+30 days)**

## Key Issues Are All Manageable

**MicroCosm orbit determination software modification to process GPS data from s/c with data from ground tracking sites**
**Different from QuikScat**
**Within capabilities of software**
**Experts at CCAR can do**
**Groundtrack monitoring and maneuver design software modifications and adaptations:**
**Maneuvers to change between calibration and mission orbits**
**Inclination maneuvers**
**Filtering of long-period perturbations**
**More difficult than previous application of this s/w to GFO because of lower altitude and tighter groundtrack repeat band**
**Experts at Raytheon can do**
**Off-nadir pointing software**
**Develop algorithms and software to meet accuracy requirement (done)**
**Develop automated system with required interfaces to produce quaternions for spacecraft pointing commands**
**Experts at CCAR and Ball can do**

## Risk Analysis and Mitigation - Ball’s Approach to Risk

**Risk analysis at Ball assessed as the combined effects of:**
**Likelihood of occurrence**
**Impact of occurrence**
** **
** **
**Likelihood****	****	****	****Impact****	****	****	****Rating**
**Requires new technology****	****Mission cannot be ****	****3**
**or process****	****	****	****accomplished**
**Requires extrapolation of****	****Degraded system****	****	****2**
**existing technology****	****	****performance**
**Requires established****	****	****No system effect****	****	****1**
**technology**
**Product of likelihood and impact is the overall risk factor used for ranking risk and prioritizing mitigation**

## Risk Analysis and Mitigation -FDS Risks are All Low

**Numerical risk****	****Qualitative risk****	****Action**
**factor****	****	****assessment**
**1, 2, 3****	****	****low****	****	****monitor**
**4, 6****	****	****	****medium****	****	****establish mitigation plan**
**9****	****	****	****	****high****	****	****avoid with alternative design**
** **
**For ICESat Flight Dynamics:**
**Likelihood of occurrence for all risk issues is low (1)**
**Impact of occurrence for all risk issues ranges from low (1) to high (3)**
**Overall risk factors (product of likelihood and impact) are from 1 to 3**
**In low risk range - action is to accept and monitor**

## Concept of Operations - Immediately After Launch

## Concept of Operations - Routine Ops

## FDS Schedule - System Installed and Tested Six Months Before Launch

## Special Topics

**Orbit determination and propagation requirements derivation**
**Orbit determination and propagation analysis**
**Off-nadir pointing**

## Operational Orbit Determination -Requirements Derivation

**Purpose of this requirement - need sufficient orbit determination accuracy to monitor orbit evolution and plan maintenance maneuvers **
** **
**GFO experience is relevant to ICESat**
**Similar orbit maintenance requirements**
**Exact Repeat Orbit**
**Repeat band +/- 0.8 km vs. 1.0 km**
**Altitude 600 km vs. 800 km**
**GFO maintains node crossing only; not inclination**
**GFO Operational Orbit Determination (from Doppler data) accuracy (r,t,n) ~ 1 m, 2.5 m, 2.5 m**
**Propagation accuracy after 1 day ~270 m along track (at burn time)**
**GFO success in maintaining orbit suggests that ICESat requirements should be similar**
**Relatively coarse orbit determination requirements**

## Derivation of Orbit Determination Requirements - Philosophy

**Don’t want requirement to be more stringent than necessary**
**Especially if difficult or costly to meet**
** **
**GFO can do with relatively coarse OOD accuracy**
**Use groundtrack location and drift rate to design maintenance maneuvers**
**Rather than absolute value of orbit elements or Cartesian position and velocity**
**Example:**
**A 1 mm/s velocity change -- very difficult to observe in OD solution**
**Produces a 2 m change in SMA -- easier to observe in OD solution**
**Produces a 16 m/day change in groundtrack drift rate -- easy to observe in successive OD solutions**
**Groundtrack location and drift rate is a much more sensitive measurement - less accuracy required**

## More Orbit Determination Philosophy and Requirements

**Interested only in groundtrack location and drift -- not in actual values of orbit elements or position and velocity**
**Don’t have to know elements or Cartesian position and velocity accurately**
**Can simply observe groundtrack location and drift rate**
**Maneuvers designed based on groundtrack location and drift rate**
**Can apply a very precise velocity change (mm/s) (to accurately change the groundtrack drift rate) without knowing the actual s/c velocity to comparable accuracy**
**Accuracy of velocity change much better than knowledge of actual velocity**
** **
**Operational Orbit Determination accuracy requirements (r,t,n):**
**1 m, 5 m, 1 m**

## Orbit Propagation Requirements - Without Maneuver

**Purpose of this requirement - be able to plan maneuvers to maintain orbit**
**GFO orbit determination accuracy (r,t,n) ~(1 m, 2.5 m, 2.5 m)**
**Propagation accuracy after 1 day ~ 270 m in along track direction (due to 1 m radial error); radial and across track components similar to OD accuracy**
**Propagation error mostly in along track component due to drag mismodeling)**
**This accuracy is sufficient for GFO maneuver planning**
**Should also be sufficient for ICESat**
** **
**Orbit Propagation Without Maneuver accuracy requirement (r,t,n):**
**One day of propagation**
**10 m, 1 km, 10 m**

## Orbit Propagation Requirements - With Maneuver

**Purpose of this requirement - be able to point communication antennas to close link**
**EPGS antenna beamwidth = 0.8 deg (0.4 deg half cone angle)**
**Maps to 4.2 km error when tracking at zenith**
**Decreases quickly with elevation angle**
** **
**Orbit Propagation With Maneuver accuracy requirement (r,t,n):**
**One day of propagation after a maneuver**
**4 km, 4 km, 4 km**

## Orbit Determination and Propagation Accuracy

**Accuracy of orbit determination and propagation analyzed by Hyung-Jin Rim at the University of Texas**
**Analysis performed in response to questions raised at flight dynamics working group meeting last January in Austin**
**Simulation assumptions:**
**Atmospheric drag worst case**
**Airplane mode (maximum A/m)**
**Maximum solar activity for mid-2001 launch**
**Solar panels articulating at orbit rate**
**Piecewise constant drag parameter estimated (linear fit to individual drag parameters used for propagation)**
**Expected at-launch gravity errors (no tuning)**
**GPS tracking data; carrier phase data used**
**GPS receiver characteristics similar to the BlackJack receiver**
**Simulated fit over 2 and 3 days, plus propagation for 18 hrs with and without 10 minute “snapshots” of GPS data**

## Orbit Determination Accuracy - Results

**UT simulation results (rms to fitted orbit over 2 days):**
**Radial = 0.74 m**
**Along track = 1.89 m**
**Across track = 0.43 m**
**3D rss = 2.07 m**
**Results for 3 day fit very similar - accuracy not sensitive to arc lengths in this range**
** **
**Requirements are (r,t,n) = (1 m, 5 m, 5 m)**

## Orbit Propagation Accuracy - Results

**UT simulation results (maximum error over 2 day prediction):     **
**                            ****radial          along track       across track    **
**2 day fit               10.5 m            450.6 m              30.5 m**
**3 day fit                7.6 m             103.6 m              7.0 m**
** **
**To convert these maximum errors to 1****s**** values after one day of propagation:**
**Assume maximum errors are 3****s**** values**
**Two day propagation error assumed to be twice the one day error**
**1****s**** errors after one day of propagation:**
**Radial = 1.8 m**
**Along track = 75 m**
**Across track = 5.1 m**
** **
**Requirements are (r,t,n) = (10 m, 1 km, 10 m) after one day**

## Off-Nadir Pointing Will Produce Better Science

**Spacecraft will be rolled about nadir to point at the reference groundtrack to within 30 m**
**Better science - will measure elevation of the same line of spots each overflight**
**Can detect elevation changes in less time (years less)**
**Approximately a sinusoidal roll each orbit with magnitude < 0.1 deg**
**Pointing algorithm and software developed by CCAR, under contract to ICESat (reports and conference paper published)**
**Implementation and simulation subject of a Special Study by Ball (SER published)**
** **
**This off-nadir pointing will be done constantly - every day, all the time**
**Except when observing targets of opportunity**
**System will be highly automated**

## Off-Nadir Pointing -Procedure  and Features

**Procedure:**
**Obtain OOD solutions, propagate forward**
**CCAR s/w calculate time series of ECI quaternions to point at reference groundtrack**
**Insert quaternions into fixed frame ECI target tables**
**Upload and execute **
** **
**Features:**
**Calculate and upload 36 hours of roll commands once each day**
**Point at nadir between 60 deg S and 60 deg N (to save memory space)**
**Point at reference groundtrack above 60 deg latitude**
**New pointing quaternion each minute**
**Results is ~745 targets uploaded per day**
**Fits in 1024 element target table **
**Can probably upload target table and CSM on a single pass**
**Can upload full target table in 4.25 minutes**
**Verified very quickly with a checksum command**

## Off-Nadir Pointing -Simulation

**CCAR generated quaternions **
**One orbit modeled**
**Corresponds to 1 km node offset - conservative**
**Input to Ball attitude simulator (Matlab)**
**Resulting groundtrack location compared to reference (ideal) groundtrack**
**Resulting groundtrack error rms = 24.6 m**
**Due to:**
**Command granularity ~ 2 m**
**ACS maneuver profiler ~ 24.5 m**
**See plots**
** **

## Off-Nadir PointingMatlab Results

## Off-Nadir Pointing - Simulation Results

## Off-Nadir Pointing - Pointing Error Budget

## Off-Nadir Pointing - Results Can Be Improved

**Total error of 27.6 m meets 30 m requirement**
**We don’t plan on trying to improve (lack of funds; meets requirement)**
**Largest error component of 24.5 m due to ACS maneuver profiler**
**S/C attitude control system smoothes maneuvers from one commanded attitude to the next**
**Could probably be improved**
**ECI targeting (this application) not used previously with RS2000 or BCP 2000 ADCS system**
**Not optimized for highest accuracy**
** **
**If optimized - error could perhaps be reduced to ~15-20 m (factor of two improvement - better science?)**

## Conclusions

**ICESat FDS based extensively on reuse of QuikScat and GFO**
**Review of all FDS requirements**
**Design compliant with all requirements; demonstrated by similarity (reuse) or analysis (orbit determination, off-nadir pointing)**
**Interfaces are well-defined**
**Simplified because of co-location with the MOC**
**Reuse of LASP-MMFD and LASP-EPGS interfaces**
**Interface to Science Team via the MOC archive**
**Two trades complete (s/w); no more planned **
**High quality personnel working on project**
**Key issues are all manageable**
**Risks are low**
**Concept of operations straightforward extension of QuikScat**
**Schedule aims for complete, tested system in early 2001**