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NASA to launch space observatory that will map 450M galaxies

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Re: NASA to launch space observatory that will map 450M galaxies

#11

Post by perihelions »

dylan604 wrote: post #7

"The SPHEREx mission will map the entire sky four times over two years, offering scientists a chance to study how galaxies form and evolve, and providing a window into how the universe came to be." So each object will be scanned ~6 months from the previous scan. How much evolving within the universe will be noticeable within that 2 year run? My gut response is not much, but that's why we do the science to see the cha…

They're talking about galaxy evolution in the early universe, over timescales of millions of years. Statistics measured across the (large) sample group, not within one galaxy. Scroll down to "It will classify galaxies according to redshift accuracy..."

Re: NASA to launch space observatory that will map 450M galaxies

#12

Post by Sanzig »

dylan604 wrote: post #7

"The SPHEREx mission will map the entire sky four times over two years, offering scientists a chance to study how galaxies form and evolve, and providing a window into how the universe came to be." So each object will be scanned ~6 months from the previous scan. How much evolving within the universe will be noticeable within that 2 year run? My gut response is not much, but that's why we do the science to see the cha…

Why would coolant be a consumable? These things are usually cooled with Stirling cryocoolers which are closed systems.

Re: NASA to launch space observatory that will map 450M galaxies

#13

Post by perihelions »

Sanzig wrote: post #12
dylan604 wrote: post #7

"The SPHEREx mission will map the entire sky four times over two years, offering scientists a chance to study how galaxies form and evolve, and providing a window into how the universe came to be." So each object will be scanned ~6 months from the previous scan. How much evolving within the universe will be noticeable within that 2 year run? My gut response is not much, but that's why we do the science to see the cha…

Why would coolant be a consumable? These things are usually cooled with Stirling cryocoolers which are closed systems.

I did a quick search and it seems there is neither?

- "SPHEREx relies on an entirely passive cooling system — no electricity or coolants are used during normal operations"

https://www.jpl.nasa.gov/news/6-things-to-know-about-spherex...

edit to add:

- "The telescope is passively cooled to below 80 K in low-Earth orbit by three nested V-groove radiators. An additional radiator cools the long wavelength focal plane temperature below 60 K to reduce detector dark current."

https://arxiv.org/abs/2404.11017v1

Re: NASA to launch space observatory that will map 450M galaxies

#15

Post by niwtsol »

dylan604 wrote: post #7

"The SPHEREx mission will map the entire sky four times over two years, offering scientists a chance to study how galaxies form and evolve, and providing a window into how the universe came to be." So each object will be scanned ~6 months from the previous scan. How much evolving within the universe will be noticeable within that 2 year run? My gut response is not much, but that's why we do the science to see the cha…

To answer three of your questions:

- It is passively cooled rather than using an expendable coolant- "SPHEREx relies on an entirely passive cooling system — no electricity or coolants are used, simplifying the spacecraft’s design and operational needs."

- It is a Medium-Class Explorers (MIDEX) mission - Investigations characterized by definition, development, mission operations, and data analysis costs not to exceed $180 to $200 million total cost to NASA. I think the cost of ground support eats into the budget length. The original estimate for project was $241M, so it was a large MIDEX

- It is in a Polar orbit around Earth at the day-night (terminator) line

https://www.jpl.nasa.gov/press-kits/spherex/

https://explorers.gsfc.nasa.gov/missions.html

https://spaceflightnow.com/2019/02/14/nasa-selects-mission-t...

Re: NASA to launch space observatory that will map 450M galaxies

#16

Post by dylan604 »

Sanzig wrote: post #12
dylan604 wrote: post #7

"The SPHEREx mission will map the entire sky four times over two years, offering scientists a chance to study how galaxies form and evolve, and providing a window into how the universe came to be." So each object will be scanned ~6 months from the previous scan. How much evolving within the universe will be noticeable within that 2 year run? My gut response is not much, but that's why we do the science to see the cha…

Why would coolant be a consumable? These things are usually cooled with Stirling cryocoolers which are closed systems.

Every system I'm familiar with that used liquid nitrogen to cool the IR instruments has had a operational lifespan based on the coolant. JWST is one such. "The coolant will slowly vaporize, limiting the lifetime of the instrument from as short as a few months to a few years at most."[0]

[0]https://en.wikipedia.org/wiki/James_Webb_Space_Telescope

Re: NASA to launch space observatory that will map 450M galaxies

#17

Post by jessriedel »

Sanzig wrote: post #12
dylan604 wrote: post #7

"The SPHEREx mission will map the entire sky four times over two years, offering scientists a chance to study how galaxies form and evolve, and providing a window into how the universe came to be." So each object will be scanned ~6 months from the previous scan. How much evolving within the universe will be noticeable within that 2 year run? My gut response is not much, but that's why we do the science to see the cha…

Why would coolant be a consumable? These things are usually cooled with Stirling cryocoolers which are closed systems.

As another comment mentions, SPHEREx is passively cooled. But fwiw, plenty of infrared space telescopes use consumable coolant:

> Notable infrared missions that carried consumable cryogen include IRAS (1983), ISO (1995–1998), Spitzer (2003–2009 in cryo mode), Herschel (2009–2013), WISE (2009–2011 in cryo mode), and Planck (2009–2013). Each relied on a finite liquid helium (or solid hydrogen) supply to keep detectors cold and reverted to a warmer operating mode or ended once their coolant was depleted.

Re: NASA to launch space observatory that will map 450M galaxies

#18

Post by dylan604 »

perihelions wrote: post #13
Sanzig wrote: post #12

Earlier quoted context omitted.

Why would coolant be a consumable? These things are usually cooled with Stirling cryocoolers which are closed systems.

I did a quick search and it seems there is neither? - "SPHEREx relies on an entirely passive cooling system — no electricity or coolants are used during normal operations" https://www.jpl.nasa.gov/news/6-things-to-know-about-spherex... edit to add: - "The telescope is passively cooled to below 80 K in low-Earth orbit by three nested V-groove radiators. An additional radiator cools the long wavelength focal plane temp…

The Spitzer used passive cooling, but only as a method to reduce the amount of coolant required. It still needed a coolant.

"One of the most important advances of this redesign was an Earth-trailing orbit.[1] Cryogenic satellites that require liquid helium (LHe, T ≈ 4 K) temperatures in near-Earth orbit are typically exposed to a large heat load from Earth, and consequently require large amounts of LHe coolant, which then tends to dominate the total payload mass and limits mission life. Placing the satellite in solar orbit far from Earth allowed innovative passive cooling. The sun shield protected the rest of the spacecraft from the Sun's heat, the far side of the spacecraft was painted black to enhance passive radiation of heat, and the spacecraft bus was thermally isolated from the telescope. All of these design choices combined to drastically reduce the total mass of helium needed, resulting in an overall smaller and lighter payload, resulting in major cost savings, but with a mirror the same diameter as originally designed. This orbit also simplified telescope pointing, but did require the NASA Deep Space Network for communications"[0]

[0]https://en.wikipedia.org/wiki/Spitzer_Space_Telescope

Re: NASA to launch space observatory that will map 450M galaxies

#19

Post by perihelions »

jessriedel wrote: post #17
Sanzig wrote: post #12

Earlier quoted context omitted.

Why would coolant be a consumable? These things are usually cooled with Stirling cryocoolers which are closed systems.

As another comment mentions, SPHEREx is passively cooled. But fwiw, plenty of infrared space telescopes use consumable coolant: > Notable infrared missions that carried consumable cryogen include IRAS (1983), ISO (1995–1998), Spitzer (2003–2009 in cryo mode), Herschel (2009–2013), WISE (2009–2011 in cryo mode), and Planck (2009–2013). Each relied on a finite liquid helium (or solid hydrogen) supply to keep detectors…

Notably those were all far-infrared telescopes, which need even lower temperatures (liquid helium) to escape thermal noise.

Re: NASA to launch space observatory that will map 450M galaxies

#20

Post by niwtsol »

FirmwareBurner wrote: post #2

> four suitcase-sized satellites Americans will use anything else but the metric system :)

The PUNCH mission features four 140-pound small satellites, each about 1-by-2-by-3 feet in size.

Or

The PUNCH mission features four 63.5 kg small satellites, each about 0.3048 m × 0.6096 m × 0.9144 m in size.

https://blogs.nasa.gov/spherex/2025/03/04/nasas-spherex-punc...

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