# Notes on Astro2020 Decadal Survey Report
###### tags: `Astronomy` `OutReach&Education`

[Press livestream](https://vimeo.com/644513900)
[Interactive Summary](https://nap.edu/resource/26141/interactive/)

## What is Decadal Survey?
A super large meeting every 10 years. Giving "advice" to NASA, NSF and DOE which they have to follow. Affect how tens of billions USD goes in the next few decades.


Many famous project were recommanded by decadal survey before such as:
* VLA (1960)
* VLA/HST (1970)
* Chandra/VLBA (1980)
* Spitzer/SOFIA/ALMA (1990)
* JWST/ALMA (2000)
* WFIRST/Rubin (2010).

## Science Topics Chosen

### Pathways to Habitable Worlds (Exoplanets)
Requiring:
* Ground-based ELTs equipped with high-resolution spectroscopy, high-performance AO, and high-contrast imaging
* A large space-based IR/O/UV telescope with **high contrast** imaging and spectroscopy.
* X-ray: High spatial and spectral resolution to probe stellar activity across the entire range of stellar types

### New Windows on the Dynamic Universe (Multimessenger and physics)
Requiring:
* Transient sources: Get brightness and spectra ASAP.
* ELTs: Light coincident with mergers
* A next-generation radio observatory to detect the jets produced by NS and BH.
* NG CMB telescopes: Search for CMB polarization by inflation.
* Upgrades ground base GR and neutrino observatories.

### Unveiling the Drivers of Galaxy Growth (Galactic Ecosystem)
Requiring:
* ELTs: Galaxies in the young universe.
* NG radio: Mapping emission lines of molecular gas.
* NG IR/O/UV space telescope: Details of the nearby, evolved universe.
* FIR / X-ray: Look into hearts of dusty galaxies to reveal enshrouded black holes / tracing the hottest gas phases.
* Investments in theory to realize a new scientific foundation for understanding galaxy evolution.

## Space telescopes
### The proposals: The New Great Observatories


### HabEx
Super Hubble with star shade.


Mock observation of a system 8 pc away with exo-Earth [a], a sub-Neptune planet [b] and a Jupiter analog [c], Saturn analogs [d], and a close-in Neptune [e].

### LUVOIR
Ultra Hubble (in terms of wavelength coverage)
Super JWST (in terms of telescope design)


### Lynx
Super Chandra.



### Origins
Ultra Spitzer.



### Result

#### Highest priority
Astro2020 suggest a 6-meter UV-NIR telescope.
Similar to a smaller version of LUVOIR but with similar capability of a larger HabEx.
Set to launch on the first half of 2040s.

#### Why not choosing LUVOIR or HabEx directly?
* Not believing LUVOIR-B (8m) can be launch in 2040
* 4 m mirror (HabEx) is not enough


Technical and scientific maturization should also go with Far-IR and X ray.

## Ground base telescopes

### TMT and GMT
Credit: [US-ELTP/NOIRLab/TMT/GMT/NSF/AURA](https://www.tmt.org/page/astro2020)

#### Expected Performance
Credit: [Cmglee](https://en.wikipedia.org/wiki/File:Comparison_optical_telescope_primary_mirrors.svg)

* Resolution: 0.01"-0.02" with A.O.
*

#### Current Status
ESO EELT is doing good.
TMT suffers Hawai local people protest. Pa lama suffers volcano eruptions.
#### Astro2020 Suggestion
NSF should help and invest more into TMT and GMT.

### CMB S4
* B mode polarization
* Southern sky map at 0.1-1 cm with unprecedented sensitivity.

### ngVLA
Replacement for VLA and VLBA array in US.
Need continuous maturation program.

Credit: NRAO, NRCC

### SOFIA
Not good science but as expensive as HST/Chandra => Terminate 2023 to save money.

Credit: NASA/Jim Ross

## Summary