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Posted: Fri Mar 30, 2012 10:44 am
Hopefully we'll get some traffic on this forum as a result of that recent email from that busybody AAS/HEAD secretary.
To prime the pump, I'll put out there that the current activities of the study are all in evaluating nominal mission concepts via studies at the Goddard Mission Development Lab. These 'nominal' missions include a calorimeter (XMS-type) mission, a grating (XGS-type) mission, and a wide-field CCD (WFI-type) mission. All are somewhat smaller than the original IXO concepts, but still maintain much of the original science that IXO was to have done using these detectors.
Re: Recent news
Posted: Fri Mar 30, 2012 3:30 pm
Here is more detail on the current activity:
As stated in the original RFI call the intent of this study was to establish the highly-rated Decadal IXO science that could be accomplished at different price points from $300M to $2B. This is to be accomplished by formulating several “notional” missions based in part on the RFI input. AXSIO was a scaled-down version of IXO that incorporated only a calorimeter and a retractable grating. It was studied at the GSFC mission design lab (MDL) in Oct/Nov 2011. This study included a Price-H cost of $1.9B and is the highest cost point of this study.
The study support team and community science team (CST) have settled on our three notional missions. Small working groups have been established for each, involving both CST and support team members. So far two design lab runs have been complete: an Instrument Design Lab (IDL) run for the X-ray calorimeter to attempt to reduce its size and cost, and a Mission Design Lab (MDL) run for the notional gratings mission described below. In the follow five weeks there will be two more MDL runs, one each for the other notional missions, and a “delta” MDL run reserved for significant mission changes to ensure that the notional missions stay within the intended cost buckets.
Notional mission 1:
A calorimeter only mission with the following specs:
Effective area: 5000 cm2 at 1 keV, 2000 cm2 at 6 keV
Field of view: 4 arcmin
Bandpass: 0.2-10 keV
Angular resolution: 10” HPD with goal of 5”
Spectral resolution: at least some pixels at <2 eV at low count rates
High count rate capability desired (~ 15,000 cps with < 10% deadtime)
Mission life: 3 years, 5 year goal
Target Cost bin $1B
We have a notional mirror design, with focal length 9.5 m and diameter 1.26 m. This is a scaled down version of the AXSIO mirror, with focal length reduced to the shortest possible that still meets the 6 keV effective area and diameter reduced but still meeting the 1 keV effective area. The MDL for this mission is scheduled for the week of April 2-6.
Notional mission 2:
A gratings only mission with the following specs:
Bandpass 0.2-1.3 keV
Effective area: 500-1000 cm2 over band
Spectral resolution: >3000 over band
Mission life: 3 years
Orbit: LEO or L2
Target Cost bin ≤$600M
The working group has agreed to develop a common instrument envelope (dimensions, mass, power) that accommodates either the off-plane or the critical-angle transmission (CAT) design. Iterations between the two designs have led to the selection of a 7 m focal length system. The baseline mirror design provides margin over the required effective area. There is a desire to have the mirror/grating design modular enough that the effective area can easily modified by adding (or removing) modules. .
The team has decided to baseline an L2 orbit, which requires ~600 cm2 of mirror+grating+CCD effective area (compared with ~1000 cm2 in LEO). One possibility for the delta MDL week is to determine the changes needed for a LEO mission and the associated cost difference.
The team developed the specifications of the common envelope and the MDL run last week (March 19-23) assessed both the off-plane and CAT grating versions of the mission.
Notional mission 3:
A wide field mission with the following specs:
Effective area: 7000 cm2 at 1 keV, 2000 cm2 at 6 keV
Field of view: ≥24 arcmin
Mission life: 3 years
Orbit: LEO or L2
Target Cost bin: <$1B
The working group has just finished investigating instrument configurations incorporating 1, 2 and 3 telescopes. It was decided to use the 3-telescope design for the MDL run, largely because it represents a different configuration from the other concepts. The mirrors employ a wide-field polynomial design. Each of the three identical mirrors has a 6 m focal length and a flat angular resolution of ~7 arcsec across a 1 degree field of view. The effective area of the ensemble is about 9000 cm2 at 1 keV and 2000 cm2 at 6 keV. Each of the three identical focal planes will consist of an array of CCD chips covering the full degree field of view. For consistency with the other two notional missions, it was decided to baseline an L2 orbit.
The focal plane will be costed in two ways: adapting the CCD detectors IXO/AXSIO grating CCD detector cost estimates (and input from the grassroots estimates the Wide-Field X-ray Telescope (WFXT) RFI input), and adapting the IXO WFI cost estimate for an active pixel sensor array.
The single telescope design has dimensions in between those of AXSIO and notional mission 1. Such a system meets, but does not exceed, the field of view requirement. In parallel with the MDL run, the single telescope design will be costed by scaling from AXSIO and notional mission 1, by adjusting the mirror properties and replacing the focal planes with a wide field imager. This exercise will make possible a cost comparison between the two designs.
For all three missions, careful comparison with the IXO science goals will be carried out. This will be done via taking simulations done for the various missions that came in via the RFI, where applicable, and via new simulations when required.
Re: Recent news
Posted: Sun Oct 22, 2017 11:21 am
That's fascinating stuff. Thanks for an interesting read guys.