Talk:Nancy Grace Roman Space Telescope

Same Lagrangian L2 orbit as Webb?

So this telescope and James Webb Space Telescope will both be at L2? I'm curious if any word on how close they will be, or how they are kept from collision. Tom Ruen (talk) 07:21, 20 February 2016 (UTC)

This page [1] says WFIRST will be in geosynchronous orbit, close to the earth, not L2. Is the Reference system Sun–Earth L2 wrong in the stat table? Tom Ruen (talk) 07:32, 20 February 2016 (UTC)

And here from 4/24/2014 [2] "The SDT considered both geosynchronous and Sun-Earth L2 (2nd Lagrange point, further from the sun than the Earth) orbit options and selected a 28.5 inclined, geosynchronous orbit as the baseline for this study. The primary factor that drove the selection of this orbit is the ability to continuously downlink data to the ground and obtain a much higher science data rate."

But here Feb 18, 2016 NASA Introduces New, Wider Set of Eyes on the Universe: Baltimore's Space Telescope Science Institute to Partner on New NASA 'Wide-View' Space Telescope says "The observatory will begin operations after traveling to a gravitational balance point known as Earth-sun L2, which is located about one million miles from Earth in a direction directly opposite the sun."

As referred to for orbits, L2 isn't a single place; both JWST and WFIRST would be in a loose orbit around L2. The scale of the orbit is around a million km and the size of the spacecraft relatively minuscule and the locations well known. During station-keeping maneuvers, it will be straightforward to avoid collisions. Dbenford (talk) 16:58, 23 February 2016 (UTC)

OK, I see on Jan 11, 2016, this article was changed with orbit changed to L2 diff. So I think this fact needs to be documented in the article, that there was a choice between two orbits, and that geosynch was picked first, and then switched to L2, and explaining WHY! Tom Ruen (talk) 11:11, 20 February 2016 (UTC)

I have added a paragraph on the Geo/L2 trade based on the 2015 Final Report, Appendix C, which documents this. Dbenford (talk) 16:58, 23 February 2016 (UTC)

Launch Vehicle, as of 2016

As stated by ULA, the Boeing Delta IV is in the process of being retired (in the next few years). A Delta IV rocket will not be available to launch a telescope in 2025. My suggestion is to list "TBD" as the rocket until a launch contract has been procured with a rocket that will still exist during this time frame. — Preceding unsigned comment added by Martin Cash (talk • contribs) 19:09, 25 July 2016 (UTC)

ULA has said they are going to phase out Delta IV, but not Delta IV Heavy: "ULA Targets 2018 for Delta 4 Phase-out, Seeks Relaxation of RD-180 Ban". Rob (talk) 10:37, 29 July 2016 (UTC)

I agree with Martin Cash. Until there is a launch contract, we should list "TBD". Cheers, BatteryIncluded (talk) 13:16, 29 July 2016 (UTC)

Will it be a Flagship Program mission

It's expensive enough - Is it now or likely to be designated a NASA Flagship Program mission ? - Rod57 (talk) 06:25, 23 May 2017 (UTC)

Update: Mission downscope 2017

Zurbuchen directs Goddard do downscope WFIRST project in scope and complexity (October 20, 2017 ): [3]. -BatteryIncluded (talk) 18:43, 13 November 2017 (UTC)

I se now it is already mentioned in the 'Status' section. Cheers, BatteryIncluded (talk) 18:52, 13 November 2017 (UTC)

Can we add a construction and test schedule

Can we add a construction and test schedule - for spacecraft, OTA and instruments, so that progress can be tracked ? Have any/all construction contracts been placed ? - Rod57 (talk) 18:18, 8 December 2019 (UTC)

Article lists 3 contracts placed in 2018 - for telescope & sensors. Nowt yet? on the Spacecraft and instruments. Not clear which instruments will be built by partners such as ESA. - Rod57 (talk) 11:50, 14 February 2022 (UTC)

Mission duration & propellant - will it be serviceable or refuellable

Will the 107 kg of on-board propellant (for attitude control and L2 halo orbit maintenance?) last just the initial 5 years, or for how long an extension ? - Rod57 (talk) 18:24, 8 December 2019 (UTC)

Not sure where that number is from; the baseline fuel load is 958kg (yes, really a ton). About half is used getting into the orbit around L2 and about half to keep it there for ten years. If I can find a public reference to this I'll post it. Dbenford (talk) 22:20, 20 May 2020 (UTC) Dbenford

@Dbenford: Thanks. I forget where I read the 107 kg, but a public ref to the 958 kg and allocation would be great. - Rod57 (talk) 09:39, 26 March 2021 (UTC)

The mission is serviceable. So probably about ten years into its operation, a lightweight tanker will fly out there and refuel Roman and Webb for another 15 years of operation.--Giftzwerg 88 (talk) 06:41, 25 April 2021 (UTC)

@Giftzwerg 88: Great to hear it is serviceable. Would be good to have a ref, so we can say what is serviceable. (Webb will be harder since it wasn't designed to be refueled in space). - Rod57 (talk) 11:56, 14 February 2022 (UTC)

Seems in 2017 WFIRST was intended to be refuellable. "... the Wide-Field Infrared Survey Telescope (WFIRST) observatory, is being designed to be refuelable."[4] - Rod57 (talk) 22:59, 5 March 2022 (UTC)

Drat - that URL now gives 404. - May have to look in Roman final report. - Rod57 (talk) 12:44, 7 November 2023 (UTC)

Why is a coronagraph on a survey telescope ?

Why is a coronagraph (for study of single star) on a wide field survey telescope ? Especially strange since JWST will have a coronagraph as well ? (Is it here as a backup in case JWST is delayed/fails ?) Why did they add an exoplanet study to a deep space survey mission ? Which NASA docs explain ? (is it in the decadal study?) - Rod57 (talk) 09:26, 26 March 2021 (UTC)

The 2018 CGI ref calls CGI a technology demonstrator, with much better spec (stellar suppression for various separation) than those on HST. (Not compared to the one on JWST?) - Rod57 (talk) 20:50, 1 January 2022 (UTC)

Changing everything to the new name is jarring/confusing when talking about history before the name change.

The name was change in 2020, but the prior history has also been edited to call it Roman but refers to the WFIRST docs. At least in the history section can we call it by its then-current name of WFIRST (as in the documents referenced)? Depending on context (especially dates), we can call it WFIRST, WFIRST/Roman, or just Roman? - Rod57 (talk) 09:37, 26 March 2021 (UTC)

No objections, so I'll try to change some. - Rod57 (talk) 12:14, 14 February 2022 (UTC)

How is it different from JWST?

This mission is quite similar to James Webb – it's an infrared telescope that will be in an L2 halo orbit. So it would be nice if the article contained a section explaining the differences between the two... perhaps in the form of a table listing the two telescopes' specifications. 2601:281:D47E:1920:5122:42BB:EED0:F063 (talk) 22:27, 16 October 2022 (UTC)

JWST has a table - we could add WFIRST/Roman to it, and notes on sensor sizes, instruments eg spectrometers & coronographs ?

Selected space telescopes and instruments

Name	Launch year	Wavelength (μm)	Aperture (m)	Cooling
Spacelab Infrared Telescope (IRT)	1985	1.7–118	0.15	Helium
Infrared Space Observatory (ISO)	1995	2.5–240	0.60	Helium
Hubble Space Telescope Imaging Spectrograph (STIS)	1997	0.115–1.03	2.4	Passive
Hubble Near Infrared Camera and Multi-Object Spectrometer (NICMOS)	1997	0.8–2.4	2.4	Nitrogen, later cryocooler
Spitzer Space Telescope	2003	3–180	0.85	Helium
Hubble Wide Field Camera 3 (WFC3)	2009	0.2–1.7	2.4	Passive and thermo-electric
Herschel Space Observatory	2009	55–672	3.5	Helium
James Webb Space Telescope	2021	0.6–28.5	6.5	Passive and cryocooler (MIRI)
WFIRST/Roman	2027	0.48–2.30	2.4	Passive & cryocooler on WFI

- Rod57 (talk) 20:51, 14 December 2023 (UTC)

References

Coolant?

Does it require coolant that would limit its working life? (I'm assuming no, if it's only out to 2 microns.) Or is the limit the fuel to keep it positioned? — kwami (talk) 19:52, 7 June 2023 (UTC)

2015 doc < WFIRST-AFTA_SDT_Report_Briefing_to_Hertz_150219_Final_RevA.pdf > says a cryocooler is added to WFI to reduce temp from 120K to 100K. Comments above talk about 5 or 10 years fuel for attitude & orbit. - Rod57 (talk) 20:25, 14 December 2023 (UTC)

thanks. — kwami (talk) 21:00, 14 December 2023 (UTC)