Simulating observations with MUSTANG-2

MUSTANG-2 is a bolometric array on the Green Bank Telescope. In this notebook we simulate an observation of the Whirlpool Galaxy (M51).

import maria
from maria.io import fetch

input_map = maria.map.load(fetch("maps/crab_nebula.fits"), nu=93e9)

input_map.plot()
print(input_map)

2025-11-21 01:57:49.631 INFO: Fetching https://github.com/thomaswmorris/maria-data/raw/master/maps/crab_nebula.fits
Downloading: 100%|████████████████| 2.00M/2.00M [00:00<00:00, 24.6MB/s]

ProjectedMap:
  shape(nu, y, x): (1, 500, 500)
  stokes: naive
  nu: [93.] GHz
  t: naive
  z: naive
  quantity: rayleigh_jeans_temperature
  units: K_RJ
    min: 0.000e+00
    max: 5.876e-02
    rms: 9.295e-03
  center:
    ra: 05ʰ34ᵐ31.80ˢ
    dec: 22°01’3.00”
  size(y, x): (8.83’, 8.83’)
  resolution(y, x): (1.06”, 1.06”)
  beam(maj, min, rot): [[0. 0. 0.]] rad
  memory: 4 MB

from maria import Planner

planner = Planner(target=input_map, site="green_bank", constraints={"el": (60, 90)})
plans = planner.generate_plans(total_duration=900, sample_rate=100)

plans[0].plot()
print(plans)

PlanList(1 plans, 900 s):
                           start_time duration    target(ra,dec)     center(az,el)
chunk
0      2025-11-21 04:57:50.814 +00:00    900 s  (83.63°, 22.02°)  (117.5°, 61.62°)

instrument = maria.get_instrument("MUSTANG-2")
print(instrument)
instrument.plot()

Instrument(1 array)
├ arrays:
│            n   FOV baseline      bands polarized
│  array1  217  4.2’      0 m  [m2/f093]     False
│
└ bands:
         name     center      width    η      NEP          NET_RJ          NET_CMB    FWHM
   0  m2/f093  86.21 GHz  20.98 GHz  0.1  15 aW√s  0.5711 mK_RJ√s  0.6905 mK_CMB√s  9.133”

sim = maria.Simulation(
    instrument,
    plans=plans,
    site="green_bank",
    map=input_map,
    atmosphere="2d",
)

print(sim)

2025-11-21 01:57:58.745 INFO: Fetching https://github.com/thomaswmorris/maria-data/raw/master/atmosphere/spectra/am/v3/green_bank.h5
Downloading: 100%|████████████████| 22.0M/22.0M [00:00<00:00, 77.9MB/s]
2025-11-21 01:57:59.626 INFO: Fetching https://github.com/thomaswmorris/maria-data/raw/master/atmosphere/weather/era5/green_bank.h5
Downloading: 100%|████████████████| 12.0M/12.0M [00:00<00:00, 51.9MB/s]

Simulation
├ Instrument(1 array)
│ ├ arrays:
│ │            n   FOV baseline      bands polarized
│ │  array1  217  4.2’      0 m  [m2/f093]     False
│ │
│ └ bands:
│          name     center      width    η      NEP          NET_RJ          NET_CMB    FWHM
│    0  m2/f093  86.21 GHz  20.98 GHz  0.1  15 aW√s  0.5711 mK_RJ√s  0.6905 mK_CMB√s  9.133”
├ Site:
│   region: green_bank
│   timezone: America/New_York
│   location:
│     longitude: 79°50’23.28” W
│     latitude:  38°25’59.16” N
│     altitude: 825 m
│   seasonal: True
│   diurnal: True
├ PlanList(1 plans, 900 s):
│                            start_time duration    target(ra,dec)     center(az,el)
│ chunk
│ 0      2025-11-21 04:57:50.814 +00:00    900 s  (83.63°, 22.02°)  (117.5°, 61.62°)
├ '2d'
└ ProjectedMap:
    shape(stokes, nu, y, x): (1, 1, 500, 500)
    stokes: I
    nu: [93.] GHz
    t: naive
    z: naive
    quantity: rayleigh_jeans_temperature
    units: K_RJ
      min: 0.000e+00
      max: 5.876e-02
      rms: 9.295e-03
    center:
      ra: 05ʰ34ᵐ31.80ˢ
      dec: 22°01’3.00”
    size(y, x): (8.83’, 8.83’)
    resolution(y, x): (1.06”, 1.06”)
    beam(maj, min, rot): [[0. 0. 0.]] rad
    memory: 4 MB

tods = sim.run()
tods[0].plot()

2025-11-21 01:58:00.314 INFO: Simulating observation 1 of 1
Constructing atmosphere: 100%|████████████████| 8/8 [00:00<00:00,  8.74it/s]
Generating turbulence: 100%|████████████████| 8/8 [00:00<00:00, 22.35it/s]
Sampling turbulence: 100%|████████████████| 8/8 [00:03<00:00,  2.32it/s]
Computing atmospheric emission: 100%|████████████████| 1/1 [00:00<00:00,  1.06it/s, band=m2/f093]
Sampling map: 100%|████████████████| 1/1 [00:08<00:00,  8.48s/it, band=m2/f093, channel=(0 Hz, inf Hz), stokes=I]
Generating noise: 100%|████████████████| 1/1 [00:00<00:00,  1.05it/s, band=m2/f093]
2025-11-21 01:58:28.436 INFO: Simulated observation 1 of 1 in 28.11 s

from maria.mappers import BinMapper

mapper = BinMapper(
    center=input_map.center,
    frame="ra/dec",
    width=10 / 60,
    height=10 / 60,
    resolution=0.05 / 60,
    tod_preprocessing={
        "window": {"name": "hamming"},
        "remove_modes": {"modes_to_remove": [0]},
        "remove_spline": {"knot_spacing": 60, "remove_el_gradient": True},
    },
    map_postprocessing={
        "gaussian_filter": {"sigma": 1},
        "median_filter": {"size": 1},
    },
    units="uK_RJ",
    tods=tods,
)

output_map = mapper.run()

2025-11-21 01:58:34.812 INFO: Inferring mapper stokes parameters 'I' for mapper.
Preprocessing TODs: 100%|████████████████| 1/1 [00:01<00:00,  1.52s/it]
Mapping band m2/f093: 100%|██████████| 1/1 [00:02<00:00,  2.99s/it, stokes=I, tod=1/1]
2025-11-21 01:58:39.365 INFO: Ran mapper for band m2/f093 in 2.998 s.

output_map.plot()
output_map.to_fits("/tmp/simulated_mustang_map.fits")