PDS_VERSION_ID                    = PDS3  /* Version 3.8 February 27, 2009 */
RECORD_TYPE                       = STREAM
LABEL_REVISION_NOTE               = "2015-05-07 JUNO: Janssen    Revision 2;
                                     2017-06-04 JUNO: Janssen    Revision 3"

OBJECT                            = INSTRUMENT
  INSTRUMENT_ID                   = "MWR"
  INSTRUMENT_HOST_ID              = "JNO"

  OBJECT                          = INSTRUMENT_INFORMATION
    INSTRUMENT_NAME               = "MICROWAVE RADIOMETER"
    INSTRUMENT_TYPE               = "RADIOMETER"
    INSTRUMENT_DESC          = "


  Instrument Host Overview
  =========================

The Microwave Radiometer (MWR) is one of a suite of instruments on Juno.
The Juno mission has the overall goal of answering the outstanding questions
outstanding about Jupiter's structure and origin. Specifically, the MWR was
designed to characterize Jupiter's atmosphere as following:

   -  Determine the global O/H ratio (water abundance) in Jupiter's
      atmosphere
   -  Measure latitudinal variations in Jupiter's deep atmosphere
      (composition, temperature, cloud opacity, and dynamics)
   -  Measure the microwave brightness temperatures of Jupiter over all
      latitudes at wavelengths that fully sample the atmospheric thermal
      emission at all altitude levels from the ammonia cloud-forming
      region to below the water cloud-forming region

To achieve this the MWR experiment uses a microwave sounding approach
described in Janssen et al., 2005. The MWR instrument measures the
atmospheric thermal emission at six frequencies. Thermal emission from an
atmosphere arises because of the presence of absorbing constituents in the
atmosphere, and the measured emission contains information on both the
concentration and temperature of these constituents. The information content
changes with frequency, and the determination of the spectrum of atmospheric
thermal emission can be used to infer key parameters of both the temperature
and compositional structure of the atmosphere. Water and ammonia are the only
significant sources of microwave opacity in Jupiter's atmosphere, so their
concentrations are the unique target of any microwave sounding approach.

The MWR instrument comprises what are essentially six independent
radiometers, each of which measures the microwave emission viewed through its
own independent antenna. The six antennas are distributed around the
spacecraft body and view in a direction perpendicular to the spin axis of the
spacecraft.  Since the spin axis of the spacecraft is oriented approximately
perpendicular to the orbit plane, the beam of each antenna sweeps through a
great circle on the sky that passes along the sub-spacecraft track on Jupiter
and through the nadir direction.  Each point along this track is thus
observed numerous times, at different emission angles, as the spacecraft
spins and moves along its orbit.  The accumulated data at each such point and
its dependence on emission angle an frequency is then analyzed to obtain
vertical atmospheric composition and structure using a radiative transfer
model.

Each receiver makes contiguous radiometric measurements, or integrations, of
fixed 100-ms duration. In a typical sequence of such integrations an internal
switch is cycled from the antenna input to periodically view an internal
load, and three independent internal reference noise sources are periodically
switched on and off for calibration. The cycle for such switching is
synchronous for all receivers and is set by selecting from a table contained
in the flight software. The table may be changed by an uplink command. The
choice of specific sequences depends on instrument performance and
optimization of the calibration algorithm.

For the key observations to be made in the nine-hour window around Jupiter
perijove, the MWR is desiged to downlink all contiguous 100-ms observations.
Outside this window, however, not all of this data is essential and in most
cases the resulting data would quickly fill the MWR's partition on the
spacecraft. To avoid this, a command is sent to downlink only a fraction of
the data obtained. The instrument organizes its data stream into time-
contiguous units of ten 100-ms observations, each thus corresponding to one
second's worth of observation. Successive units may be contiguous in time
(full data rate) or separated by n seconds each (reduced data rate). A
different on-board switching sequence is typically commanded in order to
optimize the calibration for reduced sampling rates.

Documents that describe the major components of the MWR instrument and its
operation will be found in the DOCUMENTS folder and include:
   1. The MWR volume SIS
   2. The MWR instrument paper (Janssen et al., 2017)
   3. The MWR Operations Guide (not yet available)
   4. The MWR Instrument Users Guide
   5. The MWR Flight Software Users Guide
   6. The MWR Algorithm and Theoretical Basis Document and Error Analysis

The canonical paper that describes the design, operation, calibration, and
analysis of the MWR data to achieve the scientific objectives of the MWR
experiment is Janssen et al., 2017."


  END_OBJECT                      = INSTRUMENT_INFORMATION

  OBJECT                          = INSTRUMENT_REFERENCE_INFO
    REFERENCE_KEY_ID              = "JANSSENETAL2005"
  END_OBJECT                      = INSTRUMENT_REFERENCE_INFO

  OBJECT                          = INSTRUMENT_REFERENCE_INFO
    REFERENCE_KEY_ID              = "JANSSENETAL2017"
  END_OBJECT                      = INSTRUMENT_REFERENCE_INFO

END_OBJECT                        = INSTRUMENT

END