Gendreau, Keith

NASA Technical Reports Server

https://ntrs.nasa.gov/search.jsp?R=20120016975 2019-08-30T23:18:37+00:00Z
• Neutron-star Interior Composition ExploreR 
• Mission naming 
• People 
• Mission commonality 
• Goals 
- Navigation 
• Ground testbed 
- Communication 
• Challenges 
• Future activity 
Station Explorer for X-Ray Timing and Navigation Technology (SEXTANT) 
NASA GSFC 
, 
• Address NASA and National 
Academy of Sciences strategic 
questions 
• Resolve the nature of ullra-dense matter at 
the threshold of collapse to a black hole 
• Structure-Reveal the nature of matter in 
the interiors of neutron stars 
• Dynamics- Uncover the physics 
responsible for the dynamic behavior of 
neutron stars 
• Energetics-Determine how energy is 
extracted from neutron stars 
Station Explorer for X-Ray T1ming and Navigation Technology (SEXTANT) 
NASA GsFC , 
• NICER - Neutron-star Interior Composition ExploreR 
• ISS ELC Explorer Payload (2016/09/02) 
• Observe pulsars in X-ray part of EM spectrum 
• Determine pulsar radii and masses 
• SMD selected pure/yon science (Phase A) 
• SEXTANT - Station Explorer for X-Ray 
Timing and Navigation Technology 
• Same instrument used for NICER 
• Navigation (XNAV) and communication (XCOM) 
• XCOM: payload is X-ray receiver 
• XNAV: advanced algorithms, measurement processing 
• Enhanced avionics/algorithms required over NICER baseline 
Station Explorer for X-Ray Timing and Navigation Technology (SEXTANn 
NASA GsFC • 
' NICER 
• Keith Gendreau, Zaven 
Arzoumanian , Fotis Gavriil 
' XNAV 
• Jason Mitchell, Monther Hasouneh, 
John Gaebler, Dennis Woodfork, 
Luke Winternitz, Jennifer Valdez 
' XCOM 
• Wai Fong, Victor Sank, David Fisher 
' And many, many more! 
• many external partners too! 
Porlion of XNAV rfUlm 
Station Explorer for X-Ray TIming and Navigation Technology (SEXTANT) 
NASA GSFC • 
". 
" (.' . ~. 
" :,' 
XCOM 
.fav Communication 
Station Explorer for X-Ray Timing and Navigation Technology (SEXTANn 
NASA GSFC • 
Station Explorer for X-Ray Timing and Navigation Technology (SEXTANT) 
NASA GSFC 7 
• Precise timing enables improved navigation 
• Pulsars: rapidly spinning neutron stars 
• Millisecond pulsars (MSPs) 
• rival atomic clocks as time-keepers 
• accuracy & stability 
• Potentially provide galaxy-wide time-base CnIb Pulsar(sIowed), Csmbridge UnNersity. Lucky Image Group 
• GPS-like navigation capability throughout solar system 
• Measurement 
• Precisely time tag X-ray photons 
• Pulse arrival time, i.e., pulsar pseudo-range 
• Stitch sequence together for autonomous navigation solution 
• Interested agencies: NASA, DoD (DARPA), NIST 
Station Explorer for X·Ray Timing and Navigation Technology (SEXTANT) 
NASA GSFC • 
• Provide 1st on-orbit demo of XNAV concept 
• LEO worst case scenario 
• Real-time 1 D range < 1 km from 2-3 pulsars I orbit 
• XNAV-only 3D position to -500 m @ 1 day 
• Understand sky distribution effect on dilution of 
precision 
• Long-term characterization of pulsar clock stabilities 
• Characterization of additional candidate pulsars 
• Other benefits 
• Active X-ray timing observatory. RXTE 
decommissioned 
• Improved sensitivity over RXTE. XMM-Newton 
Station Explorer for X-Ray Timing and Navigation Technology (SEXTANT) 
NASA GSfC 
-
, 
• Improved X-ray concentrator optics 
• Large collecting area, small volume 
.• Silicon drift detectors 
• Time resolution < 200 ns 
• Algorithms 
• Relativistic time-transfer, pulsar range 
• GSFC Navigator GPS technology 
• Precise reference to UTe 
• MSP Emulator 
• Miniaturized modulated X-ray source 
• EDU time-tagging X-ray photon detector 
Station Explorer for X-Ray Timing and Navigation Technology (SEXTANn 
NASA GSFC " 
• Guided incremental multi-milestone development plan 
• Leverages Goddard GN&C (Code 590) software tools 
• Mission design: General Mission Analysis Tool (GMAT) 
• Orbit determination: 
• Orbit·determination toolbox (ODTBX) for MATLAB 
• Goddard Enhanced On-board Navigation System (GEONS) flight software 
• GPS receiver (Navigator GPS) design and expertise 
• Support algorithm development & testing 
• Prepare & transition algorithms to flight software 
• Standardized interfaces defined to foster collaboration 
Station Explorer for X-Ray Timing and Navigation Technology (SEXTANT) 
NASA GSFC 11 
Real-time MSP emulation 
Station Explorer fOf' X-Ray TIming and Navigation Technology (SEXTANT) 
NASA GSFC 12 
Range: 25 to 1000 kin 
Station Explorer for X-Ray Timing and Navigation Technology (SEXTANT) 
NASA GSFC 13 
Free Space 
X-Rays 
Station Explorer for X-Ray Timing and Navigation Technology (SEXTANT) 
NASA GSFC 
• Launch: HTV or Dragon 
• Huzzah to SpaceX 
• Address Crab PSR high photon count rates 
• Observing sufficient photons from low-count-rate pulsars 
• accurate measurements challenging in high dynamics 
• Choice of coordinate time 
'TDB vs. TCB 
• GPS and timing accuracy on ISS 
• Multi-path effects from geometry 
• SV visibility & geometry 
• High time accuracy 
Station Explorer for X-Ray Timing and Navigation Technology (SEXTANT) 
NASA GSFC " 
• Complete Step 2 concept study report 
• Due mid-Sep 2012 
• Demonstrate GXL T, real-time, hardware-in-the-Ioop 
• Broad improvements to modeling fidelity 
• Extensive algorithm testing 
• EDU hardware integration 
• Flight software development & integration 
• SIC integration & test 
Station Explorer for X-Ray Timing and Navigation Technology (SEXTANT) 
NASA GSFC " 


Pulsar Navigation and X-ray Communication Demonstrations with the NICER Payload on the ISS

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