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 Crab Nebula (M1).

import maria

input_map = maria.map.get("maps/m1.h5")

input_map.plot(nu_index=[0, 1, 2])
print(input_map)

2026-03-20 19:41:56.133 INFO: Fetching https://github.com/thomaswmorris/maria-data/raw/master/maps/m1.h5
Downloading: 100%|████████████████| 4.54M/4.54M [00:00<00:00, 80.7MB/s]

ProjectionMap:
  shape(stokes, nu, y, x): (1, 3, 805, 787)
  stokes: I
  nu: [149.8962 214.1375 272.5386] GHz
  t: naive
  z: naive
  quantity: rayleigh_jeans_temperature
  units: K_RJ
    min: -2.429e-02
    max: 3.824e-01
    rms: 3.907e-02
  center:
    ra: 05ʰ34ᵐ31.95ˢ
    dec: 22°00’52.16”
  size(y, x): (13.42’, 13.12’)
  resolution(y, x): (1”, 1”)
  beam(maj, min, rot): (0 rad, 0 rad, 0 rad)
  memory: 30.41 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      2026-03-20 21:04:30.006 +00:00    900 s  (83.63°, 22.01°)  (117°, 61.35°)

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  571.1 uK_RJ√s  690.5 uK_CMB√s  9.133”

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

print(sim)

2026-03-20 19:42:08.774 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, 153MB/s]
2026-03-20 19:42:09.538 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, 148MB/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  571.1 uK_RJ√s  690.5 uK_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      2026-03-20 21:04:30.006 +00:00    900 s  (83.63°, 22.01°)  (117°, 61.35°)
├ '2d'
└ ProjectionMap:
    shape(stokes, nu, t, y, x): (1, 3, 1, 805, 787)
    stokes: I
    nu: [149.8962 214.1375 272.5386] GHz
    t: [1.77403572e+09]
    z: naive
    quantity: rayleigh_jeans_temperature
    units: K_RJ
      min: -2.429e-02
      max: 3.824e-01
      rms: 3.907e-02
    center:
      ra: 05ʰ34ᵐ31.95ˢ
      dec: 22°00’52.16”
    size(y, x): (13.42’, 13.12’)
    resolution(y, x): (1”, 1”)
    beam(maj, min, rot): (0 rad, 0 rad, 0 rad)
    memory: 30.41 MB

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

2026-03-20 19:42:10.545 INFO: Simulating observation 1 of 1
Constructing atmosphere: 100%|████████████████| 8/8 [00:01<00:00,  6.86it/s]
Generating turbulence: 100%|████████████████| 8/8 [00:00<00:00, 20.50it/s]
Sampling turbulence: 100%|████████████████| 8/8 [00:04<00:00,  1.96it/s]
Computing atmospheric emission: 100%|████████████████| 1/1 [00:00<00:00,  1.20it/s, band=m2/f093]
Sampling map:   0%|                | 0/1 [00:04<?, ?it/s, band=m2/f093, channel=(0 Hz, 182 GHz)]/opt/hostedtoolcache/Python/3.12.13/x64/lib/python3.12/site-packages/numpy/lib/_function_base_impl.py:4596: RuntimeWarning: invalid value encountered in scalar subtract
  diff_b_a = b - a
Sampling map: 100%|████████████████| 1/1 [00:08<00:00,  8.85s/it, band=m2/f093, channel=(0 Hz, 182 GHz)]
Generating noise: 100%|████████████████| 1/1 [00:00<00:00,  1.09it/s, band=m2/f093]
2026-03-20 19:42:39.594 INFO: Simulated observation 1 of 1 in 29.03 s

from maria.mappers import BinMapper

mapper = BinMapper(
    tod_preprocessing={
        # "remove_modes": {"modes_to_remove": 1},
        "remove_spline": {"knot_spacing": 10, "remove_el_gradient": True},
    },
    units="uK_RJ",
    tods=tods,
    resolution=2 * input_map.resolution,
)

output_map = mapper.run()

2026-03-20 19:42:47.522 INFO: Inferring center {'ra': '05ʰ34ᵐ32.07ˢ', 'dec': '22°00’51.81”'} for mapper.
2026-03-20 19:42:47.540 INFO: Inferring mapper width 17.18’ for mapper from observation patch.
2026-03-20 19:42:47.541 INFO: Inferring mapper height 17.18’ to match supplied width.
2026-03-20 19:42:47.545 INFO: Inferring mapper stokes parameters 'I' for mapper.
Preprocessing TODs: 100%|████████████████| 1/1 [00:01<00:00,  1.61s/it]
Mapping: 100%|██████████| 1/1 [00:02<00:00,  2.09s/it, tod=1/1]

output_map.plot()