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Mission Design

Observatory in On-orbit and Launch Configurations

IXO orbit. Click the image for a larger view

IXO is a facility-class observatory that will be directly inserted into an 800,000 km semi-major axis halo orbit around the Sun-Earth L2 libration point using either an Atlas V 551 or Ariane V launch vehicle. The mission design life is five years, with consumables sized for 10 years.

IXO is built around a ~3.3 m diameter grazing-incidence mirror assembly with a 20 m focal length. When deployed during the voyage to the L2 orbit, IXO will be ~23 m tall. The observatory is divided into four major assemblies or modules: the Spacecraft Module, Deployment Module, Optics Module, and Instrument Module. For more information, refer IXO Quick Reference Guide.

Observatory Fore View

Mechanical engineering model of the IXO spacecraft, the front of the spacecraft has a sunshade for the aperture of the X-ray mirror (shown here is the slumped glass mirror concept). Click the image for a larger view

Spacecraft Module

The Spacecraft Module (SM) accommodates the bulk of the spacecraft subsystems including the power, propulsion, radio frequency (RF) communications, guidance, navigation and control, and avionics. The electronics boxes, reaction wheels, and propulsion tanks mount to a nine-sided honeycomb deck. The 6.6 m × 3.3 m diameter cylindrical composite metering structure accommodates the solar arrays, thrusters, and high-gain antenna.

Deployment Module

The Deployment Module (DM) is the portion of the metering structure which is extended on orbit. It consists of three identical ADAM masts, similar to those on NuSTAR. High precision deployment accuracy and repeatability was proven with the 60m ADAM masts used in space on SRTM. As the masts deploy, they pull with them wire harnesses and a pleated Whipple Shield type shroud assembly that shields the instruments thermally and from stray light, and provides effective protection against the micrometeoroids.

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Observatory in On-orbit and Launch Configurations

Observatory in On-orbit and Launch Configurations. Click the image for a larger view

Optics Module

The Optics Module (OM) includes the Flight Mirror Assembly (FMA), deployable sunshade, and the star tracker/TADS periscope assembly. The Optics Module interfaces the Flight Mirror Assembly to the fixed metering structure.

Observatory Aft View

Mechanical engineering model of the IXO spacecraft. The orange aft end of the spacecraft features an extendable optical bench, the instrument focal plane is at the end. Click the image for a larger view

Instrument Module

The Instrument Module (IM) accommodates the instruments. All detectors except the XGS camera mount to the Moveable Instrument Platform (MIP), which is comparable to moving platforms on Chandra and ROSAT. Focus and translation mechanisms, coupled with a Chandra heritage Telescope Aspect Determination System (TADS) for flex body metrology, assure the centering of the detectors in the converging X-ray beam, and accurate attitude reconstruction.

Module contains

The observatory design is well defined, building on studies performed over the last decade by NASA, ESA, and JAXA, and has strong heritage from previous spaceflight missions. Mission Performance Requirements are shown here. All are met or exceeded by IXO.

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Selected References

  • IXO Quick Reference Guide
  • IXO Astro2010 Decadal submissions »
  • S.L. O'Dell et al., "High-resolution x-ray telescopes", SPIE Conference 7803 Adaptive X-ray Optics, part of SPIE Optics+Photonics 2010, San Diego, CA. arXiv:1010.4892v1Download PDF
  • The International X-ray Observatory Activity submission in response to the Astro2010 Program Prioritization Panel RFI#1, 2009. Download PDF
  • Mechanical Overview of the International X-Ray Observatory, David W. Robinson, IEEE Aerospace Conference, 2009. Download PDF
  • Design Concept for the International X-Ray Observatory Flight Mirror Assembly, Ryan S. McClelland, David W. Robinson, IEEE Aerospace Conference, 2009. Download PDF
  • The Constellation-X Observatory, Jay Bookbinder et al., SPIE, 2008. Download PDF

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