| DESCRIPTION |
Instrument Overview
===================
The JIRAM instrument has a two-fold objective:
a- perform imaging of Jupiter, especially around the polar regions,
in the spectral region of 3.2-3.8 /Lm, where most of the auroral
emissions occur
b- perform co-located spectroscopy and imaging of selected regions of
Jupiter'S atmosphere in the broader 2.0-5.0 /Lm wavelength range with
medium spectral resolution.
JlRAM combines 2 data channels in one instrument: the imager and the
spectrometer, which are housed in the same optical subsystem.
JIRAM is equipped with a single telescope that accommodates both an
infrared camera and a spectrometer to facilitate a large observational
flexibility in obtaining simultaneous images in the L and M bands with
the spectral radiance over the central zone of the images.
Moreover, JIRAM will be able to perform spectral imaging of the planet
in the 2.0-5.0 m interval of wavelengths with a spectral resolution
better than 10 nm.
Instrument design, modes, and observation strategy will be optimized
for operations on-board a spinning satellite in polar orbit around
Jupiter.
The JIRAM heritage comes from Italian-made, visual-infrared imaging
spectrometers dedicated to planetary exploration, such as VIMS-V on
Cassini, VIRTIS on Rosetta and Venus Express, and VIR-MS on the Dawn
mission.
JIRAM combines two data channels in one instrument: the imager and the
spectrometer, which are housed in the same optical subsystem.
The instrument is composed of the Optical Head (OH) and the Main
Electronic (ME).
The ME contains the electronics to drive the Focal Plane Arrays (FPAs)
and compensating mirror, and perform the acquisition and conversion of
the science and housekeeping data. It also manages the operation of
the two channels, gathers data and housekeeping information from them,
stores the data, performs data compression, and interfaces the
instrument with the spacecraft.
The single ME box contains the Digital Processing Unit, the proximity
(detector driver and readout board), the main (CPU board) electronics,
the power supply, and the limited angle de spinning mechanism driver
board.
OPERATIONAL MODES
=================
JIRAM FSW manages different operations, organised for operating modes
as follows:
PROM SW modes
Initialization mode (INI)
SW Maintenance mode (SWM)
Safe mode (SAF)
Stand-by mode (STB)
Science mode (SCI)
Calibration mode (CAL)
INITIALIZATION MODE
===================
At the start-up (or after any reset), the instrument executes the INI
mode, where all the preliminary operations necessary for the nominal
working (HW and SW initialisation, memory checks, etc.) are executed
(Primary Boot). At the end of the Primary Boot the instrument is able
to check TC and send TM via the LSSL. The Secondary Boot is performed
after the reception of the proper TC.
SW MAINTENANCE MODE
====================
The SWM mode is commanded from INI to allow the direct access to the
on board RAM and EEPROM memories which can be modified and checked to
allow SW patching and parameters
SAFE MODE
=========
The SAF mode is commanded from SWM or INI mode after the successfully
loading of the EEPROM SW (Secondary Boot). The IR detectors are Off.
This mode can be entered (commanded or autonomously)
by all the EEPROM. This mode can be accessed by all the modes.
STAND-BY MODE
=============
The STB mode is commanded from SAF. In this mode the detectors are
on to allow thermal stabilization. The instrument is ready to receive
command to set and select the operative modes (SCI, CAL). The mode is
autonomously entered at the end of each acquisition sequence.
SCIENCE MODE
============
In the SCI mode the instrument performs a Science Session according to
the parameters received in STB. The main tasks are: NADIR acquisition
time evaluation based on SC Dynamics, IR commanding, data
pre-processing, data compression, data packetization
and transmission via HSSL\LSSL to SC, de-spinning mirror motor command
to compensate the SC rotation. Several sub-modes are selectable to
combine the capabilities of the two IR detectors (the first for
images,the second for spectra).
Simulated sub-modes are implemented too (I0S0 60 00).
Data from the S/C are trasmitted in sub-frames. Each detector full
active areas is split into 6 sub-frames.
OPERATIVE MODE
==============
SCI_I0_S1: Science, no IMAGE, SPECTRUM (256x336) High Spatial and High
SCI_I0_S2:
Science, no IMAGE, SPECTRUM (64x336) High Spatial and Low Spectral
SCI_I0_S3:
Science, no IMAGE, SPECTRUM(16x336) High Spatial and very Low Spectral
SCI_I1_S0:
Science, IMAGE(256x432) full acquisition, no SPECTRUM
SCI_I1_S1:
Science, IMAGE(256x432) full acquisition, SPECTRUM (256x336) High
Spatial and High spectral
SCI_I1_S2:
Science, IMAGE(256x432) full acquisition, SPECTRUM (64x336) High
Spatial and Low spectral
SCI_I1_S3:
Science, IMAGE(256x432) full acquisition, SPECTRUM (16x336) High
Spatial and Low spectral
SCI_I2_S0: Science, IMAGE(128x432) M-Band, no SPECTRUM .
SCI_I2_S1: Science, IMAGE(128x432) M-Band, SPECTRUM(256x336) High
Spatial and High Spectral.
SCI_I2_S2: Science, IMAGE(128x432) M-Band, SPECTRUM (64x336) Medium
Spatial and High Spectral
SCI_I2_S3: Science, IMAGE(128x432)
M-Band, SPECTRUM (16x336) Low Spatial and High Spectral
SCI_I3_S0: Science, IMAGE(128x432) L-Band, no SPECTRUM
SCI_I3_S1: Science, IMAGE(128x432) L-Band, SPECTRUM (256x336)
High Spatial and High Spectral
SCI_I3_S2: Science, IMAGE(128x432) L-Band, SPECTRUM(64x336) Medium
Spatial and Hogh Spectral
SCI_I3_S3: Science, IMAGE(128x432) L-Band, SPECTRUM (16x336)
Low Spatial and Hogh Spectral
CALIBRATION
===========
The calibration procedure provides a standard sequence of 6
measurements described in Table 11. The specific the meaning of the
steps is the following:
1 - the detectors look at the internal calibration unit where the
calibration sources are in the off state, the integration time is
fixed;
2 - the detector is acquired with an integration time virtually equal
to 0 (actually 20 ?s);
3 - one of the calibration source is turned on and powered with a
previously defined current, integration time is as in step 1;
4 - the same calibration source is turned on and powered with a
previously defined current but higher than in step 3 to produce a
different level of signal, integration time is as in step 1;
5 - same of step 1;
6 - same of step 2.
OPERATIVE MODE
==============
CAL_I0_S1: Calibration, no IMAGE, SPECTRUM (256x336) High Spatial and
High Spectral
CAL_I0_S2: Calibration, no IMAGE, SPECTRUM (64x336) Medium Spatial and
High Spectral
CAL_I0_S3: Calibration, no IMAGE, SPECTRUM(16x336) Low Spatial and
very High Spectral
CAL_I1_S0: Calibration, IMAGE(256x432) full acquisition
(L and M images), no SPECTRUM
CAL_I1_S1: Calibration, IMAGE(256x432) full acquisition (L and M
images), SPECTRUM (256x336) High Spatial and High spectral
CAL_I1_S2: Calibration, IMAGE(256x432) full acquisition (L and M
images), SPECTRUM (64x336) Medium Spatial and High spectral
CAL_I1_S3: Calibration, IMAGE(256x432) full acquisition (L and M
images), SPECTRUM (16x336) Low Spatial and High spectral.
CAL_I2_S0: Calibration, IMAGE(128x432) M-Band, no SPECTRUM
CAL_I2_S1: Calibration, IMAGE(128x432) M-Band, SPECTRUM (256x336) High
Spatial and High Spectral
CAL_I2_S2: Calibration, IMAGE(128x432) M-Band, SPECTRUM (64x336)
Medium Spatial and High Spectral
CAL_I2_S3: Calibration, IMAGE(128x432) M-Band, SPECTRUM (16x336) Low
Spatial and High Spectral
CAL_I3_S0: Calibration, IMAGE(128x432) L-Band, no SPECTRUM
CAL_ I3_S1: Calibration, IMAGE(128x432) L-Band, SPECTRUM (256x336)
High Spatial and High Spectral
CAL_I3_S2: Calibration, IMAGE(128x432) L-Band, SPECTRUM(64x336) Medium
Spatial and High Spectral
CAL I3S3: Calibration, IMAGE(128x432) L-Band, SPECTRUM (16x336) Low
Spatial and High Spectral
|
| REFERENCES |
Adriani, A., Filacchione, G., Di Iorio, T., Turrini, D., Noschese, R., Cicchetti, A., Grassi, D.,
Mura, A., Sindoni, G., Zambelli, M., Piccioni, G., Capria, M.T., Tosi, F., Orosei, R., Dinelli, B.M.,
Moriconi, M.L., Roncon, E., Lunine, J.I., Becker, H.N., Bini, A., Barbis, A., Calamai, L.,
Pasqui, C., Nencioni, S., Rossi, M., Lastri, M., Formaro, R. and Olivieri, A., JIRAM, the
Jovian Infrared Auroral Mapper, Space Science Reviews, https://doi.org/10.1007/s11214-014-0094-y, 2017.
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