Geoscience Reference
In-Depth Information
Besides these regular observations, we will execute the dark current
acquisition of about 20-30 s during flights on the night-side at least once
a week. Moreover, for the important or interesting areas that are out
of the nominal observation, we will plan extra observations with con-
sideration of allowed data amount and prediction of data reduction by
compression.
4. Overview of TC Ground Processing Systems
4.1.
Level 2A processing system
The SELENE data will be transmitted to the SELENE Operation and
Analysis Center (SOAC) in the Institute of Space and Astronautical Sci-
ence (ISAS) at Sagamihara from USDS and stored in the level 0/1 (L0/1)
processing system in the SOAC (see Fig. 2). When the data arrive at the
L0/1 processing system, a notification message is mailed to the LISM level
2A (L2A) processing system in Channel Access Data Unit (CADU) format.
When the L2A processing system receives the mail, it starts running to get
the LISM data that is divided into Virtual Channel Data Unit (VCDU)
with a mission ID of LISM. The L2A processing system extracts LISM
data with the Consultative Committee on Space Data Systems (CCSDS)
packet format from data in VCDU. A CCSDS packet is composed with a
primary header, secondary headers, user data, and a check word that is
optional. The extracted LISM data in CCSDS packet are depacketed and
separated into TC, MI, and SP data.
In the L2A processing system, a number will be attached in a sequen-
tial TC data taken in a set of same parameters. This number is called as
a “strip” number. The strip number is sequentially attached by each rev-
olution. The TC strip numbers are given without distinguishing telescope
systems and same strip numbers are given for the stereo observation. The
data divided into unit of strip will be thereafter cut into “scenes” by a
definite line number with an overlap. The planned line numbers of net and
overlap are 4088 and 568 in default, respectively. Since the nominal active
pixel number for TC is 3500 (and two dummy pixels for DCT compres-
sion), the total volume of a TC scene data processed in L2A processing
system will be about 20 MB. The TC data in scene unit are re-compressed
by 12 bit JPEG and registered in SELENE level 2 data base (L2DB) sys-
tem in the SOAC with a thumbnail image and a catalogue information file.
Co-investigators (Co-Is) will get the SELENE mission data products via
the L2DB system.
