diff --git a/dc1/noise_sim/compress_hdf5.py b/dc1/noise_sim/compress_hdf5.py
new file mode 100755
index 00000000..24761424
--- /dev/null
+++ b/dc1/noise_sim/compress_hdf5.py
@@ -0,0 +1,173 @@
+#!/usr/bin/env python3
+
+"""
+This script loads v0 uncompressed TOAST observations and writes v1 compressed files.
+"""
+
+import os
+import sys
+import shutil
+import re
+import glob
+
+import datetime
+
+import argparse
+
+import numpy as np
+
+from astropy import units as u
+
+import toast
+import toast.ops
+
+from toast.timing import gather_timers, dump, Timer
+
+from toast.observation import default_values as defaults
+
+
+def parse_arguments():
+    """
+    Defines and parses the arguments for the script.
+    """
+    parser = argparse.ArgumentParser(
+        description="Compress CMB-S4 simulation data"
+    )
+
+    parser.add_argument(
+        "--verify",
+        required=False,
+        action="store_true",
+        default=False,
+        help="Re-load the converted data and verify consistency",
+    )
+
+    parser.add_argument(
+        "--obs",
+        type=str,
+        required=False,
+        nargs="+",
+        help="One or more observation files",
+    )
+
+    # The operators we want to configure from the command line or a parameter file.
+    operators = list()
+
+    # Parse all of the operator configuration
+    config, args, jobargs = toast.parse_config(parser, operators=operators)
+
+    return config, args, jobargs
+
+
+def main():
+    env = toast.utils.Environment.get()
+    log = toast.utils.Logger.get()
+    env.enable_function_timers()
+    global_timer = toast.timing.GlobalTimers.get()
+    global_timer.start("compress HDF5 (total)")
+
+    config, args, jobargs = parse_arguments()
+
+    # Default group size
+    comm = toast.Comm()
+
+    # Process each observation
+    for obs_path in args.obs:
+        obs_dir = os.path.dirname(obs_path)
+        file_root = os.path.splitext(obs_path)[0]
+        if comm.world_rank == 0:
+            print(f"Working on {obs_path}:")
+        backup = f"{file_root}_uncompressed.h5"
+        timer = Timer()
+        timer.start()
+        obs = toast.io.load_hdf5(
+            obs_path,
+            comm,
+            process_rows=comm.group_size,
+            meta=None,
+            detdata=None,
+            shared=None,
+            intervals=None,
+            detectors=None,
+            force_serial=False,
+        )
+
+        if comm.comm_world is not None:
+            comm.comm_world.barrier()
+        timer.stop()
+        if comm.world_rank == 0:
+            print(f"  Load {obs_path} in {timer.seconds()} s", flush=True)
+
+        if comm.world_rank == 0:
+            os.rename(obs_path, backup)
+        
+        if comm.comm_world is not None:
+            comm.comm_world.barrier()
+        
+        timer.start()
+        obf = toast.io.save_hdf5(
+            obs,
+            obs_dir,
+            meta=None,
+            detdata=[
+                (defaults.det_data, {"type": "flac"}),
+                (defaults.det_flags, {"type": "gzip"}),
+            ],
+            shared=None,
+            intervals=None,
+            config=None,
+            times=defaults.times,
+            force_serial=False,
+        )
+        if comm.comm_world is not None:
+            comm.comm_world.barrier()
+        timer.stop()
+        if comm.world_rank == 0:
+            print(f"  Save {obs_path} in {timer.seconds()} s", flush=True)
+
+        if obf != obs_path:
+            msg = f"Generated HDF5 ({obf}) does not match original "
+            msg += f"file name ({obs_path})"
+            raise RuntimeError(msg)
+
+        if args.verify:
+            timer.start()
+            compare = toast.io.load_hdf5(
+                obs_path,
+                comm,
+                process_rows=comm.group_size,
+            )
+            if comm.comm_world is not None:
+                comm.comm_world.barrier()
+            timer.stop()
+            if comm.world_rank == 0:
+                print(
+                    f"  Re-load {obs_path} for verification in {timer.seconds()} s",
+                    flush=True
+                )
+
+            if compare != obs:
+                msg = f"Observation HDF5 verify failed:\n"
+                msg += f"Input = {obs}\n"
+                msg += f"Loaded = {compare}"
+                log.error(msg)
+                raise RuntimeError(msg)
+            elif comm.world_rank == 0:
+                print(f"  Verification PASS", flush=True)
+        else:
+            if comm.world_rank == 0:
+                print(f"  Skipping verification", flush=True)
+
+    # Dump all the timing information to the output dir
+
+    global_timer.stop("compress HDF5 (total)")
+    alltimers = gather_timers(comm=comm.comm_world)
+    if comm.world_rank == 0:
+        out = os.path.join(".", "timing")
+        dump(alltimers, out)
+
+
+if __name__ == "__main__":
+    world, procs, rank = toast.mpi.get_world()
+    with toast.mpi.exception_guard(comm=world):
+        main()
diff --git a/dc1/noise_sim/compress_hdf5.slurm b/dc1/noise_sim/compress_hdf5.slurm
new file mode 100644
index 00000000..58c2ff25
--- /dev/null
+++ b/dc1/noise_sim/compress_hdf5.slurm
@@ -0,0 +1,68 @@
+#!/bin/bash
+#SBATCH --qos=regular
+#SBATCH --time=05:00:00
+#SBATCH --nodes=1
+#SBATCH --job-name=CMBS4_todcompress
+#SBATCH --licenses=SCRATCH
+#SBATCH --constraint=cpu
+#SBATCH --account=mp107
+
+# set parent directory corresponding to one frequency band
+PARENT_DIRECTORY="/global/cfs/cdirs/cmbs4/dc/dc0/staging/noise_sim/outputs_rk/LAT0_CHLAT/f090"
+
+# set range of observations to compress by this script (inclusive)
+START_INDEX=1
+END_INDEX=30
+
+echo "Listing all observations in $PARENT_DIRECTORY"
+
+# list all observations in parent directory and save to a variable
+SUBDIR_LIST=$(find "$PARENT_DIRECTORY" -mindepth 1 -maxdepth 1 -type d | sort)
+# extract observations names for printing to console
+SUBDIR_NAMES=$(echo "$SUBDIR_LIST" | xargs -I{} basename {})
+echo "Observations found: "
+echo "$SUBDIR_NAMES"
+
+echo "Proceeding to compress observations indexed in range: $START_INDEX-$END_INDEX"
+# select subset of observations (subdirectories) based on range and save to a variable
+SELECTED_SUBDIRS=$(echo "$SUBDIR_LIST" | sed -n "${START_INDEX},${END_INDEX}p")
+# extract selected observations names for printing to console
+SELECTED_SUBDIR_NAMES=$(echo "$SELECTED_SUBDIRS" | xargs -I{} basename {})
+echo "Selected observations: "
+echo "$SELECTED_SUBDIR_NAMES"
+
+# loop through selected subdirectories and process each one
+for subdir in $SELECTED_SUBDIRS; do
+  echo "Processing observation: $(basename $subdir)"
+  # search for files with the expected starting keywords : 'RISING' or 'SETTING'
+  FILE_LIST=$(find "$subdir" -type f \( -name "RISING*" -o -name "SETTING*" \) -printf "%p ")
+  # extract file names for printing to console
+  echo "Files to compress: "
+  for filename in $FILE_LIST; do
+    echo $(basename $filename)
+  done
+
+  # call compression script on the list of files
+  date
+  echo "Calling flac compression script ..."
+  srun -n 128 python compress_hdf5.py --verify --obs $FILE_LIST > "log_$(basename $subdir).txt" 2>&1
+
+  # if python script runs without error, delete backup files
+  if [ $? -eq 0 ]; then
+    echo "FLAC compression script ran successfully. Deleting backup files..."
+    if find "$subdir" -type f -name "*uncompressed.h5" -delete; then
+      echo "Backup files deleted successfully."
+      date
+    else
+      # If backup files deletion fails for some reason we stop the everything to avoid any risk of running out of disk memory.
+      echo "Error deleting backup files. Exiting loop over observations."
+      date
+      break
+    fi
+  else
+    echo "FLAC compression script encountered an error. Not deleting any files."
+    date
+  fi
+done
+
+echo "Observation batch $START_INDEX-$END_INDEX processing in $(basename $PARENT_DIRECTORY) band done. Please verify log files."
\ No newline at end of file
diff --git a/dc1/noise_sim/convert_hdf5_to_spt3g.py b/dc1/noise_sim/convert_hdf5_to_spt3g.py
new file mode 100755
index 00000000..388d6527
--- /dev/null
+++ b/dc1/noise_sim/convert_hdf5_to_spt3g.py
@@ -0,0 +1,220 @@
+#!/usr/bin/env python3
+
+"""
+This script loads HDF5 format data and exports to SPT3G format data.
+"""
+
+import os
+import sys
+import shutil
+import re
+import glob
+
+import datetime
+
+import argparse
+
+import numpy as np
+
+from astropy import units as u
+
+import toast
+import toast.ops
+
+from toast.timing import gather_timers, dump
+
+from toast import spt3g as t3g
+from spt3g import core as c3g
+
+from toast.observation import default_values as defaults
+
+
+def parse_arguments():
+    """
+    Defines and parses the arguments for the script.
+    """
+    parser = argparse.ArgumentParser(
+        description="Convert CMB-S4 simulated HDF5 data to SPT3G format"
+    )
+
+    parser.add_argument(
+        "--obs",
+        type=str,
+        required=False,
+        nargs="+",
+        help="One or more observation directories.",
+    )
+
+    # The operators we want to configure from the command line or a parameter file.
+    operators = list()
+
+    # Parse all of the operator configuration
+    config, args, jobargs = toast.parse_config(parser, operators=operators)
+
+    return config, args, jobargs
+
+
+def main():
+    env = toast.utils.Environment.get()
+    log = toast.utils.Logger.get()
+    env.enable_function_timers()
+    global_timer = toast.timing.GlobalTimers.get()
+    global_timer.start("convert_hdf5_to_spt3g (total)")
+
+    config, args, jobargs = parse_arguments()
+
+    # Use a group size of one
+    comm = toast.Comm(groupsize=jobargs.group_size)
+
+    # Create the (initially empty) data
+    data = toast.Data(comm=comm)
+
+    # Set up temporary symlinks and output
+    nowstr = datetime.datetime.now(datetime.timezone.utc).isoformat()
+    input = f"hdf5_{nowstr}"
+    output = f"spt3g_{nowstr}"
+
+    if comm.world_rank == 0:
+        os.makedirs(input)
+        os.makedirs(output)
+
+    obsloc = dict()
+
+    for odir in args.obs:
+        obsdir = os.path.basename(os.path.normpath(odir))
+        # Look for the data file
+        obsdata = glob.glob(os.path.join(odir, "RISING*.h5"))
+        if len(obsdata) == 0:
+            obsdata = glob.glob(os.path.join(odir, "SETTING*.h5"))
+        if len(obsdata) == 0:
+            obsdata = glob.glob(os.path.join(odir, "POLE*.h5"))
+        if len(obsdata) != 1:
+            raise RuntimeError(f"Did not find exactly one data file for {odir}")
+        obsdata = os.path.abspath(obsdata[0])
+        obsdatafile = os.path.basename(obsdata)
+        obsname = re.sub(r"_\d+\.h5", "", obsdatafile)
+        obsloc[obsname] = obsdir
+        log.info_rank(
+            f"Found observation data {obsdatafile}",
+            comm=comm.comm_world
+        )
+        if comm.world_rank == 0:
+            os.symlink(obsdata, os.path.join(input, obsdatafile))
+
+    # Load the data.
+    loader = toast.ops.LoadHDF5(
+        volume=input,
+        process_rows=1,
+    )
+    log.info_rank(
+        f"Loading HDF5 data from {loader.volume}", comm=comm.comm_world
+    )
+    loader.apply(data)
+
+    # Build up the lists of objects to export from the first observation
+
+    noise_models = list()
+    meta_arrays = list()
+    shared = list()
+    detdata = list()
+    intervals = list()
+
+    msg = "Exporting observation fields:"
+
+    ob = data.obs[0]
+    for k, v in ob.shared.items():
+        g3name = f"shared_{k}"
+        if re.match(r".*boresight.*", k) is not None:
+            # These are quaternions
+            msg += f"\n  (shared):    {k} (quaternions)"
+            shared.append((k, g3name, c3g.G3VectorQuat))
+        elif k == defaults.times:
+            # Timestamps are handled separately
+            continue
+        else:
+            msg += f"\n  (shared):    {k}"
+            shared.append((k, g3name, None))
+    for k, v in ob.detdata.items():
+        msg += f"\n  (detdata):   {k}"
+        if k == "signal":
+            # We are going to convert this below.  Append
+            # the new name to the list.
+            detdata.append(("signal_f32", k, None))
+        else:
+            detdata.append((k, k, None))
+    for k, v in ob.intervals.items():
+        msg += f"\n  (intervals): {k}"
+        intervals.append((k, k))
+    for k, v in ob.items():
+        if isinstance(v, toast.noise.Noise):
+            msg += f"\n  (noise):     {k}"
+            noise_models.append((k, k))
+        elif isinstance(v, np.ndarray) and len(v.shape) > 0:
+            if isinstance(v, u.Quantity):
+                raise NotImplementedError("Writing array quantities not yet supported")
+            msg += f"\n  (meta arr):  {k}"
+            meta_arrays.append((k, k))
+        else:
+            msg += f"\n  (meta):      {k}"
+
+    log.info_rank(msg, comm=comm.comm_world)
+
+    # Convert the 8-byte detector data to 4-byte.
+
+    log.info_rank("Converting signal to 4-byte floats", comm=comm.comm_world)
+    for ob in data.obs:
+        ob.detdata.create("signal_f32", dtype=np.float32)
+        for d in ob.local_detectors:
+            ob.detdata["signal_f32"][d, :] = ob.detdata["signal"][d, :]
+        del ob.detdata["signal"]
+
+    # Export the data
+
+    meta_exporter = t3g.export_obs_meta(
+        noise_models=noise_models,
+        meta_arrays=meta_arrays,
+    )
+    data_exporter = t3g.export_obs_data(
+        shared_names=shared,
+        det_names=detdata,
+        interval_names=intervals,
+        compress=True,
+    )
+    exporter = t3g.export_obs(
+        meta_export=meta_exporter,
+        data_export=data_exporter,
+        export_rank=0,
+    )
+
+    save3g = toast.ops.SaveSpt3g(
+        directory=output,
+        framefile_mb=1000,
+        obs_export=exporter,
+        purge=True,
+    )
+
+    log.info_rank(
+        f"Exporting SPT3G data to {save3g.directory}", comm=comm.comm_world
+    )
+    save3g.apply(data)
+
+    if comm.world_rank == 0:
+        # Move spt3g outputs to the observation directories
+        for out3g in obsloc.keys():
+            os.rename(os.path.join(output, out3g), os.path.join(obsloc[out3g], "spt3g"))
+        # Remove the input symlinks
+        shutil.rmtree(input)
+
+    # Dump all the timing information to the output dir
+
+    global_timer.stop("convert_hdf5_to_spt3g (total)")
+    alltimers = gather_timers(comm=comm.comm_world)
+    if comm.world_rank == 0:
+        out = os.path.join(output, "timing")
+        dump(alltimers, out)
+
+
+if __name__ == "__main__":
+    world, procs, rank = toast.mpi.get_world()
+    with toast.mpi.exception_guard(comm=world):
+        main()