Overview of future telescopes/instruments in cosmology

[LifeIsStrange]

I have a long term objective of exhaustively and extensively mapping the soon too be, future telescopes that will reshape mankind's understanding of the universe.
This is currently a short highly incomplete draft but I will update it incrementally.

Gamma ray astronomy

Gamma ray astronomy most well known usefulness comes from measurements of the transient events Gamma Ray Bursts, which allows inferences in cosmology and highest energy physics, moreover for a long time, GRBs were the method that achieved the highest redshift observations, and this might become competitive again in the future to break the redshift barrier.
Moreover, GRBs are theorized to have events preceding them and coming after them, such as Xrays afterglows and potentially optical/radio counterparts.
Gamma ray astronomy is a large range of light frequency (Mev to > PEV).
Gamma ray astronomy is not limited to GRBs, and has many other uses, a major one being the observed gamma ray galactic center excess, being a major signature of dark matter anhiliation. Moreover advances in polarization accuracy can constrain astrophysical models.
LHAASO (and its upgrade) and the incoming CTA array ground based telescopes will allows order of magnitude(s) improvement regarding the highest energy gamma rays. As for the lower part of the spectrum, a space instrument is required,
recently SVOM, a SWIFT competitor was launched but is underpowered, sadly while there are a few space proposals, only two seems to have somewhat reliable funding/backing:

COSI: smex with a launch date for 2027
It specifically address the so called "MEV gap" meaning it will improve accuracy on low energy gamma rays, it has huge potential to prove dark matter anhiliation and btw has a polarimeter.

There is the related and extremely underappreciated topic of cosmic rays astronomy (studying electrons and atoms/antimatter coming at us instead of light). Cosmic rays astronomy has a large number of anomalies (such as the positron and antinucleon excess).
If antideuterium or antihelium 4 were found, it would be a smoking gun signature for dark matter anhiliation.
Which is the goal of the GAPS mission

A small subset of cosmic rays detectors, can be used both for cosmic rays astronomy and for gamma rays astronomy, which is the case for the GAPS successor: GRAMS (funding status unclear)

As we will see extensively in this future essay, the planned missions from ESA and NASA are not really efficient nor are they complete/exhaustive, they have missions that are considerably redundant, which is extremely sad, and simultaneously, they have major gaps, meaning that major aspects of astronomy are not planned to be improved by them in the 2020s, or even in the 2030s!
Another thing that we will contemplate, is that the actually groundbreaking science projects budgets are being cannibalized by extremely low scientific returns missions, especially by: heliophysics (study of the sun), solar system missions (mostly useless) and asteroid missions (laughably wasteful), and to some extent earth observing space instruments (NOAA, etc).
Thankfully, there are other space agencies, namely:
Japan (JAXA), Russia, China, India, Canada and the recently created United Arab Emirates Space Agency!
A comparison of their respective budgets versus their number of planned space telescopes is absolutely striking to identify the level of scientific fraud. By far the ESA is the most scientifcially efficient space agency, and that is saying a lot for a space agency that is in absolute terms, extremely inefficient and that self inflict extreme apertures limitations (small mirror size) because of their obsession with silicon carbide mirrors.
Currently the UAE has a very high budget and zero planned space telescopes, this will hopefully change in the future..
Russia has a few major projects but because of worsening budgets cuts, most are delayed (spektr UV, GAMMA-400) though I still have hopes on Spektr-M.
JAXA has very few projects, though two are extremely important (Litebird and their infrared GAIA competitor)
India has a few projects (CMB, astrosat 2), currently with zero reliable planned launch dates...
Canada nearly only project is CASTOR UV.
Therefore all alternatives space agencies, despite their combined budget far higher than the ESA, have a scientific returns while important, very selective to select topics, mostly because of fraud.
This is not true for China, which despite their budget spending being quite inefficient, china is the one saviour of astronomy and of cosmology because they fill many gaps left by ESA and NASA.

This paper is a nice overview of planned missions in cosmic rays astronomy

https://arxiv.org/abs/2301.10255

Among them, chinese HERD mission stands out, as being the most accurate cosmic ray calorimeter AND being the only high energy space based gamma ray telescope being funded, with a launch date for 2027

https://arxiv.org/abs/1407.4866

As such in 2027, Gamma ray astronomy will be nearly "solved" and it should be able to almost definitely rule out the existence of dark matter anhiliation. The same can be said for cosmic rays astronomy.
BTW a bonus point for cherenkov telescopes is that they will allow record high optical angular resolution, hence potentially improving the tolman test and models of dust attenuation.
todo paper era of dark matter astronomy

Xray astronomy (soft and hard)

Xray astronomy has some overlap with gamma rays astronomy but they are not redundant as some phenomenas are found exclusively in one of the two light regions.
While gamma ray astronomy can do some imaging, Xray imaging (and probably spectroscopy) are higher resolution. While optical and infrared instruments are better, for high energy phenomena, Xrays are complementary and can often give the best measurements.
Xray astronomy is the light region that has recently launched the most space telescopes, by far (RXTE,HMXT,IXPE,XRISM,einstein probe, SVOM, erosita)
and yet all those telescopes are nearly useless, because they are underpowered..
As we will see, telescopes improvements are always about:
improving the size of the field of view (more data, less cosmic variance)
improving the accuracy (angular resolution, sensitivity, etc) (via mirror size and/or instrument upgrades)
improving the timing resolution (for transient astronomy (supernovaes, GRBs, etc)
and the forgotten fourth: improving polarimetry accuracy
In all cases, this can applied either for the camera (photometry) and/or for the spectrometer (IFU, etc)

So xray astronomy is at the forefront of solving the most important cosmological questions and ruling out astrophysical models, especially regarding dark matter, missing baryons, matter recycling in the universe and all kinds of high energy phenomena, including black holes, neutron stars, etc.
The truth is Xray astronomy has considerably stagnated, the highest resolution xray telescope still is to this day the 25 years old Chandra!
Erosita is the first wide field of view xray telescope but its timing and spatial resolution is quite low. XRISM was too little and has a launch failure.

The first project aiming at revolutionizing xray astronomy was ESA backed LOTS, the space mission was not funded but they funded the making of the instrument, the Wide Field Monitor.
And here we have a beautiful example of international collaboration, as China as for gamma and cosmic rays, saves the field of xray astronomy by actually funding the next revolutionnary xray space telescope: the eXTP mission

The eXTP planned for 2027 (albeit rumor of a 2029 delay) use the WFM made by the ESA and combines it to three other instruments.
The end results is that eXTP revolutionize the wide field accuracy (erosita successor), the transient astronomy accuracy, AND crucially the polarization accuraccy (IXPE successor)
polarization will once and for all allow key insights on high energy astrophysical models. Moreover the combination of wide fieldness and accuracy means that the number of detected transient xray events will explode.

A recently announced, redundant and inferior (though still reusing the WFM) competitor from NASA is the strobe-X mission

eXTP and strobe-X are however not enough, as there is still the need for a true chandra successor that maximize accuracy (not just FOV, etc)
The instruments, based on new semiconductors technologies, are almost mature and are relatively cheap, despite this there is no planned chandra successor before the 2030s.. (for bureaucratic reasons)
ESA athena, NASA Lynx and AXIS are all for the 2030s, note that AXIS if selected could be funded by the new probe class mission fund, but it seems is aimed to be artificially delayed.
Therefore the most grounbreaking xray telescopes are not for this decades unless a rogue agent decides to humiliate the agencies by showing to the world what can be done via e.g. a balloon or a sounding rocket (such as the micro-X project)
However China kinds of, partially saves xray astronomy here:
Via its space mission DIXE planned for 2027 and its successor HUBS (and here)

HUBS seems to aims for even better spectral resolution than ATHENA, in some select metrics is has a >1000 times improvement which is crazy.
DIXE which is in between, seems to be the best xray spectrometer in 2027, however, sadly, those chinese telescopes are not capable or tailored to resolve point sources, meaning their high resolution will only revolutionize diffuse observations of xrays (such as the cosmic xray background, etc). Still their papers seems to shows this has considerable potential on dark matter and other key questions.

All in all, gamma rays, cosmic rays and xray astronomy will be revolutionized although likely not before 2027 for most topics (except if balloon experiments delivers)

EUV

EUV is the light band at the frontier between UV and X-rays, and is arguably one of the least explored light band in astronomy.
Past instruments have uncovered physical anomalies, possibly mediated by a unique interaction between EUV radiation with CMB photons.
https://arxiv.org/abs/astro-ph/9808139
This paper review the field and while there are missions proposals, none are funded although there are some hopes for a balloon or sounding rocket mission.
https://arxiv.org/abs/1309.2181
Note that there are actually many existing and planned EUV instruments but sadly they are all pointed at the sun for heliophysics studies.

UV

UV is also quite neglected with the exception of Hubble. There are missions proposals that should soon be launched (possibly 2025) but are likely to be delayed, such as CASTOR (2020s), spektr-UV (2030s) and Xuntian the only true LUVOIR (delayed to 2026).
Dedicated to transient astronomy is ULTRASAT (early 2026).
Possibly astrosat-2.
Dedicated to polarimetry will be POLSTAR, which could launch right not but is in search of funding..
There is also UVEX in 2030

UV astronomy, because of spectral redshift, is limited to moderate redshift (cannot go to e.g. >Z=10), however UV is higher resolution than visible which is higher resolution than NIR, moreover UV polarimetry is essential to constrain dust models and is key for studying transient phenomenas (and exoplanet habitability), crucially the first lights of a supernovae are exclusively in UV, meaning that characterizing the initial conditions of transient phenomenas often require a wide field UV telescope, which is a major omission of modern astronomy.
As such, almost all aspects of UV astronomy will be revolutionized in 2026, which should allow a true multimessenger era and understanding of cosmic dust, and record high constraints on dark energy systematics.

Visible range

A common misconception is that infrared astronomy, via e.g. JWST has dethroned visible range astronomy.
This is an oversimplification and visible range astronomy still has extreme usefulness.
Infrared main advantage is to be able to reach higher redshift (NIR being almost maxed out the next frontier being MIR, sadly JWST MIR spectroscopy is underpowered). The second advantage is that extremely bright or dust obscured zones are better imaged in IR, such as the milky way galactic center, the zone of avoidance.
Visible range main advantage is that it is 10 time more accurate than NIR, hence had JWST been fitted with the camera on my smartphone, we would have considerably better imaging of the universe (though not of the redshift frontier). Sadly this artificial limitation will remain for a long time because all planned telescopes in the 2020s (euclid, xuntian, roman, ariel) all have extremely small mirror size (for absolutely insane reasons (silicon carbide obsession for the ESA, NASA ???)), the first to break the barrier in space (unless spektr M far infrared counts, or unless the many expandable mirrors or liquid mirrors prototypes are actually funded) will be China (the biggest historic humiliation for NASA) with Tianlin arround 2035.
Sure there will be the ground based LSST, TMT and ELT, with extremely large mirrors but I am completely skeptical of their ability to bypass the atmosphere.
Even though, for artificial reasons, the best images of the universe will not be available in the 2020s besides JWST and ground based, the stage IV surveys via euclid, and others will revolutionize cosmological constraints and systematics by the virtue of the unprecedented amount of data collected thanks to gigapixels cameras. This will also revolutionize transient astronomy.
Sadly while 2024 was supposed to be the year of cosmology, almost all projects have delayed their launch dates.
Euclid DR1 data release was supposed to be in december 2024, but now only a micro release is planned for 2025 and the 2024 DR1 will actually be released in 2026. Such extreme gatekeepings and delays about data they have already collected is inept. It might be motivated because they have ireversibly broken cosmology, or because of basic bureaucracy.
The LSST will be ready in 6 months though data will probably not be published until 2026.
The ELT and TMT are facing delays.
As such wide field visible and NIR photometry which were supposed to be the nearest and most significant revolution in cosmology, are all delayed to 2026.
Large ground based spectroscopic surveys should release next year however (DESI DR2, DESI milky way, etc), they should allow major advances in stellar physics and in galactic science, and a new ALCOCK-PACZYNSKI test.

NIR and MIR

There are rhoughly no planned MIR instrument in the 2020s..
Sofia aircraft based telescope is dead..
Recently the largest ground based NIR and only MIR telescope has been built which should be helpful to study the zone of avoidance.
JWST successors are for ~2040s.........
All the aforementioned visible range wide field telescopes are delayed and have also NIR.
An exception is the wide field NIR telescope sphereX, which has a very small aperture but via an original technology, should allow record redshift precision
https://en.wikipedia.org/wiki/SPHEREx in 2025!
As for JWST (and its ineptly small lifetime) I strongly invite the reader to read the mission proposals for JWST, we are currently in cycle 3
they shows what we will discover in the next 2 years, moreover I am the first person on earth to say the obvious, JWST has already broken the redshift barrier (NOT Z=14.30 but higher than that, probably higher than Z=16 and possibly up to Z=20!), not only that but the redshift record has been broken last year. This information is not public, but can be inferred from the proposals, basically only 10 hours had been allocated at finding a Z=14 galaxy. It is only in cycle 2 (and again in cycle 3) that they have woken up and allocated a few more hours. Which is largely enough to break the record multiple times. I hope they will test the known SMACS photometric candidates.
The information is not public because somehow 10 hours of observation take them multiple years to write a paper about...
Given the proposals, not only has the redshift barrier been broken but others key constraints on dark matter (such as imaging of the bullet cluster via JWST) will give a potentially final falsification of the standard model. The papers should be published in less than a year.

FIR

The recently announced Probe class NASA mission fund aims either at xray or far IR, though most likely will opt for xray.
Spektr-M IIRC aims for FIR and will be revolutionnary given it has an aperture larger than JWST.
Hershel FIR telescope was an immense failure because a FIR telescope requires very large apertures because the longer the wavelength the lesser the resolution.

Submillimeter

Microwave

Radio astronomy

sub 30mhz astronomy

Other instruments

(PLATO, etc)