# Presentation: 325736

## Micro-Arcsecond X-ray Imaging Mission, Pathfinder (MAXIM-PF)

**May 17, 2002**

**Micro-Arcsecond X-ray Imaging Mission, Pathfinder (MAXIM-PF)**

**System Overview**

## Requirements & Assumptions
Baseline Configuration
Options Considered
Comments, Issues, Concerns

**Baseline Configuration**
**Options Considered**
**Comments, Issues, Concerns**

**Outline**

## Requirements & Assumptions Study Overview

**Mission objective**
- X-ray interferometry mission, a pathfinder to full MAXIM
**Original requirements **
- As formulated in the Prework and in K. Gendreau’s “going-in-13may02.ppt”
**Original requirements modified during the study **
- Lifetime for Phase 1: 1 yr required / 50 targets (1wk/target);
- Lifetime for Phase 2: 3 yrs required / 4 yrs goal (3 wks/target)
**Additional constraints, challenges**
- 2015 launch
**Primary purpose of this study**
- Identify mission drivers and breakpoints
- Identify technologies required
- Subsystem configuration, mass and cost estimates
**Length of study **
- 5 days

##  Requirements & Assumptions Major Driving Requirement Areas

**High precision pointing**
- Centroid image of a laser beacon for microarcsec LOS alignment
- Point by referencing microarcsec image of stars or use GPB-like microarcsec grade Super-Gyro
**Multi s/c formation flying**
- Orbital dynamics: Formation acquisition and control; Orbits; Transfer to L2
- Propulsion: Thrust needs to vary by several orders of magnitude
- ACS: Position control to microns over 100’s of m, and to cm’s over 20000 km, knowledge to microns; Retargeting issues
**Software**
- To accommodate all functions
**Verification**
- Functional and performance verification 1 g environment
**Thermal control**
- Handle two thermally very dissimilar mission Phases with one h/w
- Control to .1 degree to maintain optical figure
- “STOP” CTE effects
**Communication**
- Complex communications web: Detector to Ground; Hub to Detector; Hub to FFs; FF to FF; Rough ranging using RF

## Baseline Configuration  Experiment Overview 

**Observatory configuration**
- One Hub spacecraft, one Detector spacecraft, six Free Flyer spacecraft
- Hub communicates with Detector and the Free Flyers
- Detector communicates with ground
**Phase 1: 100 microarcsec Science**
- 2 formation flying objects at 200 km
**Phase 2: 1 microarcsec Science**
- Hub surrounded by 6 identical Free Flyers in a circle of 200-500 m, Detector at 20,000 km
- Distance from Hub to Detector: RF ranging course & time of flight for fine ranging and control (~5m)
- Align Hub and Detector using Superstartracker that centroids the image at the Detector of a LISA - like laser beacon mounted on Hub (microarcsec)
- LOS pointing: reference beacon image to image of stars in background w/ Superstartracker or use  GPB - like Super-Gyro (microarcsec)
- HUB to FF’s distance: w/ RF ranging course; Laser interferometer fine w/ corner cubes on Hub (~10 um);
- FF position: use FF startrackers (~arcsecs)looking at LED on Hub

## Baseline Configuration  Experiment Overview 

- LOS to target knowledge to ~0.1 milliarcsec (~15 microns @ 20,000 km)

- FreeFlyer S/C
- Pitch, Yaw control to ~1 arcsec
- Pitch, Yaw Knowledge to arcsecs
- Roll Control to 30 milliarcsecs

- Optics Hub S/C
- Pitch, Yaw, control to ~ 1 arcsec, roll control to arcmins
- Pitch, Yaw, Roll Knowledge to +/- 1 arcsecond

- Diagram courtesy of K. Gendreau

##  Baseline Configuration  Experiment Overview 

**Continuous full sun**
- Battery required for safe Phase only
**Transfer to L2**
- Takes up to 6 months
- All S/C are attached together
- High thrust chemical propulsion
- Transfer stage is jettisoned at L2
**Communication web**
- HUB to Free Flyers
- HUB to Detector
- All Space-Ground communications performed by Detector spacecraft
- IP, 50 Kbps; One contact day @ DSN 5 Mbps
- Ranging for collision avoidance

##  Baseline Configuration  Overview 

##  Baseline Configuration  Overview 

## Baseline Configuration Instrument Resources Summary

## Baseline Configuration Metrology System Resources Summary

## Baseline Configuration S/c Mass Summaries

## Baseline Configuration Mission Mass Summary

## Baseline ConfigurationPayload Cost [$M]

## Baseline ConfigurationHub S/c Subsystems Cost [$M]

## Baseline ConfigurationDetector S/c Subsystems Cost [$M]

## Baseline ConfigurationOne FF S/c Subsystems Cost [$M]

## Baseline Configuration Overall Cost Summary [$M]

##  Additional Issues To ConsiderSmaller RSDO Busses

**RSDO On-Ramp II in force**
**RSDO On-Ramp IV selection in process **
- Several new buses added, to increase choice
**Spectrum Astro SA 200B, Bus dry mass = 90 kg**
- Payload Power (OAV) (EOL) / Mass Limit: 86 W / 100 kg
**Orbital - Microstar, Bus dry mass = 59 kg**
- Payload Power (OAV) (EOL) / Mass Limit: 50 W / 68 kg
**Ball BCP 600, Bus dry mass = 203 kg****	**
- Payload Power (OAV) (EOL) / Mass Limit: 125 W / 90 kg
**Orbital - Leostar, Bus dry mass = 263 kg**
- Payload Power (OAV) (EOL) / Mass Limit: 110 W / 101 kg
**Surrey - Minisat 400, Bus dry mass = 207 kg**
- Payload Power (OAV) (EOL) / Mass Limit: 100 W / 200 kg
**TRW - T200A, Bus dry mass = 242 kg**
- Payload Power (OAV) (EOL) / Mass Limit: 94 W / 75 kg

** ****SA 200B**

**BCP 600**

##  Additional Issues To Consider Bigger RSDO Busses

**Swales EO-SP (new in RSDO II catalog)**
- Bus dry mass = 370 kg
- Payload Power (OAV) (EOL) / Mass : 80 W / 110kg
**Spectrum Astro SA 200HP**
- Bus dry mass = 354 kg
- Payload Power (OAV) (EOL) / Mass Limit: 650 W / 666 kg
**Lockheed Martin - LM 900**
- Bus dry mass = 492 kg
- Payload Power (OAV) (EOL) / Mass Limit: 344 W / 470 kg
**Orbital StarBus**
- Bus dry mass = 566 kg
- Payload Power (OAV) (EOL) / Mass Limit: 550 W / 200 kg
**Orbital – Midstar**
- Bus dry mass = 580 kg
- Payload Power (OAV) (EOL) / Mass Limit: 327 W / 780 kg
**Ball BCP 2000**
- Bus dry mass = 608 kg
- Payload Power (OAV) (EOL) / Mass Limit: 730 W / 380 kg

- EO-1

- Midstar

- SA200HP -DS1

##  Comments, Issues and Concerns  I&T, Requirements Verification

**Environmental verification **
- Standard, per GEVS
**Any end-to-end testing / verification of the critical subsystems is very difficult or near-impossible in a 1 g environment**
- E-E verification of orbit maintenance and formation flying capabilities near-impossible
- E-E verification of metrology system near-impossible
- E-E verification of X-ray beam focus and alignment is difficult
**Reasonable trades must be made on verification approaches, goals, and requirements**
- That alone is a very significant body of work

##  Maturity, Technologies, TRL

**MAXIM is feasible !**
- MAXIM does not factor in any unrealistic technology expectations or technologies un-envisionable today
- Fairly mature and serious plans, even for the metrology
**Still, a staggering amount of  technology development is required: **
- Metrology system: H/w and s/w elements
- Superstartracker
- GPB - like Super-Gyro for pointing
- Software
- Formation flying and “virtual-one-body” telescope control software
- Analysis and simulation techniques
- Propulsion system
- Very low thrust technologies, extremely variable force thrusters
- Verification approaches and technologies for FF LAI missions
- Simulators
- Low CTE optical/structural materials
**General TRL Level of MAXIM key technologies today is 2-3**

## Tall Poles 

**Tall Pole 1: Multi s/c formation flying**
- ACS: Position control to microns over 100’s of m, and to cm’s over 20000 km, knowledge to microns; Retargeting issues
- Orbital dynamics: Formation acquisition and control; Orbits; Transfer to L2
- Metrology System: swarm sensors, interferometric range sensors, beacon detecting attitude sensors
**Tall Pole 2: High precision pointing**
- Centroid image of a laser beacon for microarcsec LOS alignment
- Point by referencing microarcsec image of stars or use GPB-like microarcsec grade Super-Gyro
**Tall Pole 3: Software**
- To accommodate all required functions
**Tall Pole 4: Propulsion **
- Continuous smooth micro-thrusters
- Thrusters force variable by orders of magnitude

## Tall Poles

**Tall Pole 5: Verification science**
- Theoretical “risk-science” assessment on feasible verification vs. available resources
- Functional and performance verification in 1 g environment
- “STOP” CTE effects
**Tall Pole 6: Thermal control**
- Control to .1 degree to maintain optical figure
- Handle two thermally very dissimilar mission phases with one h/w
**Tall Pole 7: Communication**
- Complex communications web: Detector to Ground; Hub to Detector; Hub to FFs; FF to FF; Rough ranging using RF
**Tall Pole 8: Mirror element actuators & software**
**General TRL Level of key technologies today is 2-3**

##    Additional Issues To Consider

**Startracker on FF opposite the Hub – Sun line would stare at Sun**
- Since 6 FF’s are 60 degrees apart, roll entire formation, to have two FFs closest to Hub – Sun line at equal 30 degrees
- This concept doesn’t work for a higher number of FF’s, unless FF startracker FOV is sufficiently narrowed (complicates access to star-field)
**Structural-Optical-Thermal effects**
- Not fully addressed yet
- Thermal control to 1.5 mK required – not trivial !
- Lower CTE optical/structural materials?
**Structural stability between the attitude sensor and the instrument**
-  It is good practice to mount the attitude sensors and the instrument on a common temperature controlled optical table
**Free Flyers station fixed**
- Free Flyer station clocking position in circle around Hub is constrained
- To change position, while keeping mirrors in alignment requires rolling the FF s/c
- Rolling of FF s/c is disallowed for sun / anti-sun sides must be pointed right
- Mounting FF Mirror Assemblies on turntable would allow repositioning of any FF s/c to any station

##    Additional Issues To Consider

**Other mission orbits should be fully explored**
- Earth leading/trailing drift away orbit at .1 AU/year
- Distant retrograde orbits
- Solar-libration: “kite-like” solar sail “floating” on a toroid-like pseudo-libration surface which envelops L1 between Sun-Earth
**Calibration Plan**
- Calibration may be a major requirements driver, must be factored in early on
**Communications network architecture**
- Communications between constellation elements: much refinement is required
**TDRSS at L2? Servicing at L2?**
- Explore synergies and joint funding possibilities w/ other LAI missions at L2
**Servicability at L2**
- Design shouldn’t of the bat preclude future serviceability
- Coordinate w/ servicing planners

## Supporting Data

**Systems spreadsheet tool: “LAI-MAXIM-PF_System_Sheets.xls”**
- System configuration summaries
- Mass and cost rollups and detailed ISIS subsystem data
- Quick propulsion calculator
- Prework information
**WBS template: “Generic_WBS_Template_by_GSFC_NOO.doc”**
- Full NASA mission’s complete Work Breakdown Structure
- Compiled by GSFC New Opportunities Office
**Useful web sites**
- Access to Space at http://accesstospace.gsfc.nasa.gov/ provides launch vehicle performance information and other useful design data.
- Rapid Spacecraft Development Office at http://rsdo.gsfc.nasa.gov/ provides spacecraft bus studies and procurement services.

## System Summary

**GSFC Contact: **Keith Gendreau
**Phone Number: **301/286-6188
**Mission name and Acronym: **MAXIM-Pathfinder
**Authority to Proceed (ATP) Date: **Dec 2007
**Mission Launch Date: **2015
**Transit Cruise Time (months): **n/a
**Mission Design Life (months): **48
**Length of Spacecraft Phase C/D (months):**** **72 ** **
**Bus Technology Readiness Level (overall): **3
**S/C Bus management build: **TBD
**Experiment Mass: **3000 kg