1. GIST AND INTERACTIONS WITH
USERS
The 20th GIST meeting was held at the Environmental
Systems Science Centre, at Reading University, hosted by Prof A. Slingo, on 25-27th October 2003. This reviewed ongoing project
activities and provided a greater opportunity to view the work of the ESSC in
using GERB data. The first attendance of a representative of the Edinburgh
group demonstrated the widening interest in GERB data.
Further details on the performance of the GERB-2 instrument on MSG-1 appear
below. The minutes of the GIST meetings are available on request from the P.I.
The 21st GIST meeting will be held at the National Center
for Atmospheric Research, Boulder, Colorado, USA from 31 March to 2 April. The
meeting will be held jointly with the CERES Science Team meeting, illustrating
the strong synergy between the two experiments and teams. There are already
several joint projects, notably in the areas of directional models and in
validation. Further projects are anticipated.
2. GERB-1 INSTRUMENT
GERB-1 arrived back at RAL in July 2003. It was subsequently sent to Imperial
College for re-calibration and was returned to RAL towards the end of August of
the same year. A daughter board was designed to replace the battery, the design
of which was agreed with ESA, Alcatel and EUMETSAT. In this design, the new
emergency power source is the Nominal Survival heater supply, which is switched
either to the instrument or to the heater. The daughter board is required to accommodate
a 24V voltage regulator on an existing PCB within the IEU, to minimise the
amount of rework required within an already qualified unit.
The board was built, installed and tested successfully. A blanking plate was
made up to compensate for the mass lost due to the removal of the arming plug.
The unit was then resealed and underwent vibration and thermal vacuum testing
at the start of March 2004. It should be returned to Alcatel before the 25th
March 2004.
3. GERB-2 INSTRUMENT
GERB-2 remained in the ‘sunblock’ mode of operation
from 1438 UTC on 15th August to 1610 UTC on 3rd November for the autumn ‘sun
avoidance’ season. Earth view data are not collected in this mode. GERB
Earth-viewing operation resumed with ‘deep space’ scans, to gain more information
on the increased stray light seen near the solstices, and the next in the
series of calibration monitor observations set up to track instrument shortwave
gain. Following these, GERB has operated in ‘normal’ mode collecting Earth-view
data. As a conclusion to the programme of calibration observations, an
‘Instrument Calibration Test Review Board’ was held by telephone with EUMETSAT
on 28th October. This agreed that the programme had been completed
successfully, but that further analysis activities remained. These are, mostly,
being carried out by Imperial College and the results are feeding into the
calibration parameters used in the GERB data processing.
MSG-1 was manoeuvred to its ‘nominal’ longitude of 3.5ºW during January
14th-27th and on mid-day 29th January went operational as Meteosat-8. The GERB
instrument continued to operate in ‘normal’ mode throughout the manoeuvre
period.
The spring ‘sun avoidance’ season began on 14th February with GERB-2 now being
operated in ‘normal’ mode from 0156 to 2033 each day. During the remaining
time, operation is in ‘sunblock’ mode to prevent
damage to the GERB-2 detectors by their possible exposure to direct sunlight
near midnight. EUMETSAT have accepted this change as a result of improvements
made to both the GERB-2 and Meteosat-8 on-board safeing
software.
GERB-2 Commissioning & Operations were discussed with EUMETSAT and Imperial
College at a meeting on 25th-26th February at RAL. This reviewed the GERB
‘Flight Operations Manual’, in the light of GERB-2 commissioning experience and
the ongoing ‘emergency power’ modifications that have been made to the GERB-1
and 3 instruments, and the ‘Operations Interface Control Document’ which
defines the details of the EUMETSAT-RAL and EUMETSAT-Imperial College
operational interfaces. These interfaces are working well and should ensure the
continuing reliable operation of the GERB-2 instrument.
4. GERB-3 INSTRUMENT
The GERB-3 instrument has been through re-calibration
at Imperial College and is now in storage at RAL. The launch date for MSG-3 is
expected to be in 2012, so de-storage of GERB-3 in preparation for delivery to
the spacecraft prime contractor (TAS) is expected in 2011.
5. GERB–4 INSTRUMENT
The Delivery Review Board (DRB) for the GERB-4
instrument was held in November 2009. The instrument passed the review and is
now in storage at RAL. The launch date for MSG-4 will not be announced for some
time yet, but is not expected before 2014. Until the launch date is known
GERB-4 will remain in storage at RAL. EUMETSAT has an option to re-calibrate
GERB-4, but has not yet confirmed it wishes to take up this option.
6. GERB GROUND SEGMENT AND
OPERATIONS
6.1 Status of
the GERB Ground Segment Processing System (GGSPS)
The GERB Ground Segment Processing System (GGSPS) has continued to function
well. A spate of data-line problems before Christmas 2003 appear to have been
solved by BT and an ongoing, relatively minor, problem with the commercial
data-base system used by the GGSPS also appears to have been corrected by the
suppliers.
The geo-location problems caused by systematic errors in the on-board ‘start of
line (SOL)’ signal have become better understood. In particular, it has been
found possible to make a correction based on ‘corrected start of line (CSOL)’
information routinely generated by EUMETSAT in the SEVIRI processing. A system
to transfer these CSOL data from EUMETSAT to RAL is now in place and has been
in operation for a few weeks (as of March 10th). The changes needed to the
GGSPS system for using these data have been designed, are being coded and are
expected to be in operation by the end of March. More detailed analysis of a
sample of CSOL corrected data is showing the need for second order geo
corrections. These arise because of the changes in instrument geometry caused
by operation in the 16g environment of the spinning Meteosta-8 (these were
predicted and estimated pre-launch but operation in-orbit is allowing their
refinement). In the longer term, EUMETSAT have agreed to add the CSOL
information to the GERB telemetry stream rather than transfer these data as
separate files. This will simplify and make more reliable their association in
the GGSPS.
With the routine dissemination of SEVIRI data by EUMETSAT, the system to obtain
SEVIRI header data, via the Royal Meteorological Institute of Belgium (RMIB),
is now in use. The ‘temporary’ system, implemented between EUMETSAT and RAL to
supply data files via an ftp server, has been retired but is anticipated to be
revived for MSG-2 commissioning.
6.2 Status of
the GERB RMIB Processing System
The RMIB continues to generate GERB-2 data products. Their scientific value has
been increased considerably with the inclusion of a temporary, empirical
geo-location correction based on comparison of GERB-2 and SEVIRI data.