Add EarthFrame prior

src/jimgw/prior.py

@@ -6,6 +6,9 @@
 from flowMC.nfmodel.base import Distribution
 from jaxtyping import Array, Float, Int, PRNGKeyArray, jaxtyped
 from beartype import beartype as typechecker
+from jimgw.single_event.utils import zenith_azimuth_to_ra_dec
+from jimgw.single_event.detector import GroundBased2G, detector_preset
+from astropy.time import Time
 
 
 class Prior(Distribution):
@@ -393,6 +396,75 @@ def log_prob(self, x: dict[str, Float]) -> Float:
         return log_p
 
 
+@jaxtyped(typechecker=typechecker)
+class EarthFrame(Prior):
+    """
+    Prior distribution for sky location in Earth frame.
+    """
+
+    def __repr__(self):
+        return f"EarthFrame(naming={self.naming})"
+
+    def __init__(self, naming: str, gps: Float, ifos: list, **kwargs):
+        self.naming = ["azimuth", "zenith"]
+        if len(ifos) < 2:
+            return ValueError(
+                "At least two detectors are needed to define the Earth frame"
+            )
+        elif isinstance(ifos[0], str):
+            self.ifos = [detector_preset[ifo] for ifo in ifos[:2]]
+        elif isinstance(ifos[0], GroundBased2G):
+            self.ifos = ifos[:2]
+        else:
+            return ValueError(
+                "ifos should be a list of detector names or Detector objects"
+            )
+        self.gmst = Time(gps, format="gps").sidereal_time("apparent", "greenwich").rad
+        self.delta_x = self.ifos[1].vertex - self.ifos[0].vertex
+
+        self.transforms = {
+            "azimuth": (
+                "ra",
+                lambda params: zenith_azimuth_to_ra_dec(
+                    params["zenith"],
+                    params["azimuth"],
+                    gmst=self.gmst,
+                    delta_x=self.delta_x,
+                )[0],
+            ),
+            "zenith": (
+                "dec",
+                lambda params: zenith_azimuth_to_ra_dec(
+                    params["zenith"],
+                    params["azimuth"],
+                    gmst=self.gmst,
+                    delta_x=self.delta_x,
+                )[1],
+            ),
+        }
+
+    def sample(
+        self, rng_key: PRNGKeyArray, n_samples: int
+    ) -> dict[str, Float[Array, " n_samples"]]:
+        rng_keys = jax.random.split(rng_key, 2)
+        zenith = jnp.arccos(
+            jax.random.uniform(rng_keys[0], (n_samples,), minval=-1.0, maxval=1.0)
+        )
+        azimuth = jax.random.uniform(
+            rng_keys[1], (n_samples,), minval=0, maxval=2 * jnp.pi
+        )
+        return self.add_name(jnp.stack([azimuth, zenith], axis=1).T)
+
+    def log_prob(self, x: dict[str, Float]) -> Float:
+        zenith = x["zenith"]
+        azimuth = x["azimuth"]
+        output = jnp.where(
+            (azimuth > 2 * jnp.pi) | (azimuth < 0) | (zenith > jnp.pi) | (zenith < 0),
+            jnp.zeros_like(0) - jnp.inf,
+        )
+        return output
+
+
 @jaxtyped(typechecker=typechecker)
 class PowerLaw(Prior):
     """

src/jimgw/single_event/runManager.py

@@ -58,6 +58,7 @@ def jaxarray_representer(dumper: yaml.Dumper, data: ArrayImpl):
             )
         },
     ),
+    "EarthFrame": prior.EarthFrame,
 }
 
 

src/jimgw/single_event/utils.py

@@ -118,6 +118,7 @@ def Mc_q_to_m1m2(Mc: Float, q: Float) -> tuple[Float, Float]:
     return m1, m2
 
 
+@jit
 def ra_dec_to_theta_phi(ra: Float, dec: Float, gmst: Float) -> tuple[Float, Float]:
     """
     Transforming the right ascension ra and declination dec to the polar angle
@@ -144,6 +145,162 @@ def ra_dec_to_theta_phi(ra: Float, dec: Float, gmst: Float) -> tuple[Float, Floa
     return theta, phi
 
 
+@jit
+def euler_rotation(delta_x: tuple[Float, Float, Float]):
+    """
+    Calculate the rotation matrix mapping the vector (0, 0, 1) to delta_x
+    while preserving the origin of the azimuthal angle.
+
+    This is decomposed into three Euler angles, alpha, beta, gamma, which rotate
+    about the z-, y-, and z- axes respectively.
+
+    Copied and modified from bilby-cython/geometry.pyx
+    """
+    norm = jnp.power(
+        delta_x[0] * delta_x[0] + delta_x[1] * delta_x[1] + delta_x[2] * delta_x[2], 0.5
+    )
+    cos_beta = delta_x[2] / norm
+    sin_beta = jnp.power(1 - cos_beta**2, 0.5)
+
+    alpha = jnp.atan2(-delta_x[1] * cos_beta, delta_x[0])
+    gamma = jnp.atan2(delta_x[1], delta_x[0])
+
+    cos_alpha = jnp.cos(alpha)
+    sin_alpha = jnp.sin(alpha)
+    cos_gamma = jnp.cos(gamma)
+    sin_gamma = jnp.sin(gamma)
+
+    rotation = jnp.array(
+        [
+            [
+                cos_alpha * cos_beta * cos_gamma - sin_alpha * sin_gamma,
+                -sin_alpha * cos_beta * cos_gamma - cos_alpha * sin_gamma,
+                sin_beta * cos_gamma,
+            ],
+            [
+                cos_alpha * cos_beta * sin_gamma + sin_alpha * cos_gamma,
+                -sin_alpha * cos_beta * sin_gamma + cos_alpha * cos_gamma,
+                sin_beta * sin_gamma,
+            ],
+            [-cos_alpha * sin_beta, sin_alpha * sin_beta, cos_beta],
+        ]
+    )
+
+    return rotation
+
+
+@jit
+def zenith_azimuth_to_theta_phi(
+    zenith: Float, azimuth: Float, delta_x: tuple[Float, Float, Float]
+) -> tuple[Float, Float]:
+    """
+    Transforming the azimuthal angle and zenith angle in Earth frame to the polar angle and azimuthal angle in sky frame.
+
+    Copied and modified from bilby-cython/geometry.pyx
+
+    Parameters
+    ----------
+    zenith : Float
+            Zenith angle.
+    azimuth : Float
+            Azimuthal angle.
+    delta_x : Float
+            The vector pointing from the first detector to the second detector.
+
+    Returns
+    -------
+    theta : Float
+            Polar angle.
+    phi : Float
+            Azimuthal angle.
+    """
+    sin_azimuth = jnp.sin(azimuth)
+    cos_azimuth = jnp.cos(azimuth)
+    sin_zenith = jnp.sin(zenith)
+    cos_zenith = jnp.cos(zenith)
+
+    rotation = euler_rotation(delta_x)
+
+    theta = jnp.acos(
+        rotation[2][0] * sin_zenith * cos_azimuth
+        + rotation[2][1] * sin_zenith * sin_azimuth
+        + rotation[2][2] * cos_zenith
+    )
+    phi = jnp.fmod(
+        jnp.atan2(
+            rotation[1][0] * sin_zenith * cos_azimuth
+            + rotation[1][1] * sin_zenith * sin_azimuth
+            + rotation[1][2] * cos_zenith,
+            rotation[0][0] * sin_zenith * cos_azimuth
+            + rotation[0][1] * sin_zenith * sin_azimuth
+            + rotation[0][2] * cos_zenith,
+        )
+        + 2 * jnp.pi,
+        (2 * jnp.pi),
+    )
+    return theta, phi
+
+
+@jit
+def theta_phi_to_ra_dec(theta: Float, phi: Float, gmst: Float) -> tuple[Float, Float]:
+    """
+    Transforming the polar angle and azimuthal angle to right ascension and declination.
+
+    Parameters
+    ----------
+    theta : Float
+            Polar angle.
+    phi : Float
+            Azimuthal angle.
+    gmst : Float
+            Greenwich mean sidereal time.
+
+    Returns
+    -------
+    ra : Float
+            Right ascension.
+    dec : Float
+            Declination.
+    """
+    ra = phi + gmst
+    dec = jnp.pi / 2 - theta
+    return ra, dec
+
+
+@jit
+def zenith_azimuth_to_ra_dec(
+    zenith: Float, azimuth: Float, gmst: Float, delta_x: tuple[Float, Float, Float]
+) -> tuple[Float, Float]:
+    """
+    Transforming the azimuthal angle and zenith angle in Earth frame to right ascension and declination.
+
+    Parameters
+    ----------
+    zenith : Float
+            Zenith angle.
+    azimuth : Float
+            Azimuthal angle.
+    gmst : Float
+            Greenwich mean sidereal time.
+    delta_x : Float
+            The vector pointing from the first detector to the second detector.
+
+    Copied and modified from bilby/gw/utils.py
+
+    Returns
+    -------
+    ra : Float
+            Right ascension.
+    dec : Float
+            Declination.
+    """
+    theta, phi = zenith_azimuth_to_theta_phi(zenith, azimuth, delta_x)
+    ra, dec = theta_phi_to_ra_dec(theta, phi, gmst)
+    ra = ra % (2 * jnp.pi)
+    return ra, dec
+
+
+@jit
 def log_i0(x):
     """
     A numerically stable method to evaluate log of