SECCHI Observing Sequences
Author: Sarah
Matthews
Date: 30 July 2002
This document contains a first sample of proposed science studies
submitted by members of the UK solar physics community for use with the suite
of instruments on SECCHI. The primary instruments to be considered are the HI1
and HI2, with the purpose of determining operational requirements for these
instruments arising from the science requirements. However, other studies where
the HI instruments are not the driver have also been considered. From these
studies the main issues raised so far are:
variable cadence in both instruments, masking partial fields, pixel
summing and co-ordination with other instruments both on STEREO and on other
spacecraft.
Observation Title: Impact of
CME on the Earth
Name: Richard Harrison
Institute: RAL
E-mail: r.harrison@rl.ac.uk
Version Date: 1 May 2002
Brief Scientific Objective and Observation
Overview:
One of the
principal aims of STEREO is to enable a better understanding of the arrival and
impact of CMEs on the Earth. Thus, a major goal is the direct observation of a
CME event arriving at Earth. For this, the prime instrument here is HI2, which
has the Earth and CME within its field of view. However, the support of HI1,
COR1 and COR2 is required to provide the most complete understanding of the CME
structure and evolution as it propagates from the Sun.
EUVI: [Bands
- He II 304, Fe IX 171, Fe XII 195, Fe XV 284 Å; Resolution - 1.6 arcsec/pixel;
FOV - 0.9 deg Sun-centred; Nominal cadence 30 s]
Ø
Required (yes/no)
-
No
Ø
Which bands?
-
n/a
Ø
Image cadence?
-
n/a
Ø
FOV (full Sun,
partial Sun (define area and pointing))
- n/a
Ø
Other details
-
n/a
COR1:
[Bandpass - 650-660 nm (brightness and pB); Resolution - 7.5 arcsec/pixel; FOV
- 1.3-4.0 R (full revolution; Sun centred); Nominal cadence 20 s (3 images/min
in different polarisation angles)]
Ø
Required (yes/no)
-
Yes
Ø
Image cadence?
-
nominal
Ø
FOV (full or partial
field (define area and pointing)) - full
Ø
Other details
COR2:
[Bandpass - 650-750 nm (brightness and pB); Resolution - 15 arcsec/pixel; FOV -
2-15 R (full revolution; Sun centred); Nominal cadence 100
s]
Ø
Required (yes/no)
-
Yes
Ø
Image cadence?
-
nominal
Ø
FOV (full or partial
field (define area and pointing)) - full
Ø
Other
details
HI1: [Bandpass - 650-750 nm (brightness); Resolution - 35
arcsec/pixel;
FOV - 20o circle centred at 13.28o to Sun centre
(3.28-23.28o along ecliptic); Nominal cadence 1
hr]
Ø
Required (yes/no)
-
Yes
Ø
Image cadence?
-
nominal
Ø
FOV (full or partial
field (define area and pointing)) - full
Ø
Other
details
HI2: [Bandpass - 400-1000 nm (brightness); Resolution - 240
arcsec/pixel;
FOV - 70o circle centred at 53.36o to Sun centre
(18.36-88.36o along ecliptic); Nominal cadence 3
hr]
Ø
Required (yes/no)
-
Yes
Ø
Image cadence?
-
2 hr
Ø
FOV (full or partial
field (define area and pointing)) - see details
Other details
Cadence sized for fast (1000 km/s) CME travelling from 73 to 212 solar
radii, i.e. 27 hours to cross from inner limit to Earth. Want minimum of 10
images for fast CME.
FOV could be full field. Alternatively, for better cadence/telemetry
capability, could return field only on the Sun-ward side of
Earth.
Other Spacecraft/Instruments Required (give details of
observation)?
In-situ observations from L1 (ACE) and Earth Orbit (Cluster, Polar,
Wind).
Other relevant details?
HI2 is the key instrument here. The COR1, COR2 and HI1 instruments are
asked to operate in their nominal modes; this will support the observation.
Special Operational/Software Requirements? (i.e. requirements to feed
into operations planning and software during mission
development)
Must be able to vary the HI cadence and
have a capability to return partial fields from HI.
Observation Title: CMEs in interplanetary
space
Name: Peter Cargill
Institute: Imperial College
E-mail: p.cargill@ic.ac.uk
Version Date: 26 May 2002
Brief Scientific Objective and Observation
Overview:
To study the deformation of an ICME between 20 - 30 solar radii and 1
AU.
EUVI: [Bands
- He II 304, Fe IX 171, Fe XII 195, Fe XV 284 Å; Resolution - 1.6 arcsec/pixel;
FOV - 0.9 deg Sun-centred; Nominal cadence 30 s]
Ø
Required (yes/no)
NO
Ø
Which bands?
N/A
Ø
Image cadence?
N/A
Ø
FOV (full Sun,
partial Sun (define area and pointing)) N/A
Ø
Other
details
COR1:
[Bandpass - 650-660 nm (brightness and pB); Resolution - 7.5 arcsec/pixel; FOV
- 1.3-4.0 R (full revolution; Sun centred); Nominal cadence 20 s (3 images/min
in different polarisation angles)]
Ø
Required (yes/no)
NO
Ø
Image cadence?
N/A
Ø
FOV (full or partial
field (define area and pointing)) N/A
Ø
Other
details
COR2:
[Bandpass - 650-750 nm (brightness and pB); Resolution - 15 arcsec/pixel; FOV -
2-15 R (full revolution; Sun centred); Nominal cadence 100
s]
Ø
Required (yes/no)
YES
Ø
Image cadence?
Nominal
Ø
FOV (full or partial
field (define area and pointing)) FULL
Ø
Other details:
Required for initial ICME state at 15 Rs
HI1: [Bandpass - 650-750 nm (brightness); Resolution - 35
arcsec/pixel;
FOV - 20o circle centred at 13.28o to Sun centre
(3.28-23.28o along ecliptic); Nominal cadence 1
hr]
Ø
Required (yes/no)
YES
Ø
Image cadence? 20
minutes
Ø
FOV (full or partial
field (define area and pointing)) Full
Ø
Other details. Need
high resolution to track evolution of fast ICME (>1000 km/s at Sun so will
pass through HI1 FOV in few hours) Also expect evolution to be fastest near
Sun.
HI2: [Bandpass - 400-1000 nm (brightness); Resolution - 240
arcsec/pixel;
FOV - 70o circle centred at 53.36o to Sun centre
(18.36-88.36o along ecliptic); Nominal cadence 3
hr]
Ø
Required (yes/no)
YES
Ø
Image cadence? 1
hour
Ø
FOV (full or partial
field (define area and pointing)) Full
Other details; Cadence: see HI1 for reason for fact
cadence.
Other Spacecraft/Instruments Required (give details of
observation)?
Other relevant details?
Special Operational/Software Requirements? (i.e. requirements to feed
into operations planning and software during mission
development)
High cadence is essential at all locations in order to track fast
CMEs.
Observation Title: Understanding how L1 and SECCHI observations are
related.
Name: Peter Cargill
Institute: Imperial College
E-mail: p.cargill@ic.ac.uk
Version Date: 26 May 2002
Brief Scientific Objective and Observation
Overview:
To understand how HI observations relate to in-situ ones at L1. HI
measures plasma properties, whereas for space weather one is interested in
magnetic field. How do HI plasma measurements relate to field structure of
ICME?
EUVI: [Bands
- He II 304, Fe IX 171, Fe XII 195, Fe XV 284 Å; Resolution - 1.6 arcsec/pixel;
FOV - 0.9 deg Sun-centred; Nominal cadence 30 s]
Ø
Required (yes/no)
NO
Ø
Which bands?
N/A
Ø
Image cadence?
N/A
Ø
FOV (full Sun,
partial Sun (define area and pointing)) N/A
Ø
Other
details
COR1:
[Bandpass - 650-660 nm (brightness and pB); Resolution - 7.5 arcsec/pixel; FOV
- 1.3-4.0 R (full revolution; Sun centred); Nominal cadence 20 s (3 images/min
in different polarisation angles)]
Ø
Required (yes/no)
NO
Ø
Image cadence?
N/A
Ø
FOV (full or partial
field (define area and pointing)) N/A
Ø
Other
details
COR2:
[Bandpass - 650-750 nm (brightness and pB); Resolution - 15 arcsec/pixel; FOV -
2-15 R (full revolution; Sun centred); Nominal cadence 100
s]
Ø
Required (yes/no)
NO
Ø
Image cadence?
N/A
Ø
FOV (full or partial
field (define area and pointing)) N/A
Ø
Other details:
HI1: [Bandpass - 650-750 nm (brightness); Resolution - 35
arcsec/pixel;
FOV - 20o circle centred at 13.28o to Sun centre
(3.28-23.28o along ecliptic); Nominal cadence 1
hr]
Ø
Required (yes/no)
NO
Ø
Image cadence?
N/A
Ø
FOV (full or partial
field (define area and pointing)) N/A
Ø
Other details.
HI2: [Bandpass - 400-1000 nm (brightness); Resolution - 240
arcsec/pixel;
FOV - 70o circle centred at 53.36o to Sun centre
(18.36-88.36o along ecliptic); Nominal cadence 3
hr]
Ø
Required (yes/no)
YES
Ø
Image cadence? 3 hour
/ 1 hour
Ø
FOV (full or partial
field (define area and pointing)) Partial. Need to look at 150 - 220 Rs at
Earth with full angular view.
Other details;
Other Spacecraft/Instruments Required (give details of
observation)?
ACE (MAG and SWEPAM). Any other s/c in vicinity of
Earth.
Other relevant details?
Special Operational/Software Requirements? (i.e. requirements to feed
into operations planning and software during mission
development)
One wants to take snapshots of ICME as it passes over ACE (say). This
can take up to a day. In first instance use nominal cadence, then try shorter.
Partial field will optimize telemetry requirements.
Observation Title:3-D structure on interplanetary
CMEs
Name: Lucie
Green
Institute: Mullard Space
Science
Laboratory, UCL
E-mail:
lmg@mssl.ucl.ac.uk
Version Date: 7 June 7,
2002
Brief Scientific Objective and Observation
Overview:
The helicity content of interplanetary CMEs is currently computed
using in-situ data taken from one spacecraft crossing, under the assumption
that the structure can be well modeled by a single, twisted flux rope. A more
accurate helicity computation requires knowledge of the true 3 dimensional
structure of the interplanetary CME.
For this, coronagraph observations from more than view point need to be
combined with theoretical models.
EUVI: [Bands
- He II 304, Fe IX 171, Fe XII 195, Fe XV 284 Å; Resolution - 1.6 arcsec/pixel;
FOV - 0.9 deg Sun-centred; Nominal cadence 30 s]
Ø
Required
(yes/no) No
Ø
Which
bands?
Ø
Image
cadence?
Ø
FOV (full Sun,
partial Sun (define area and pointing))
Ø
Other
details
COR1:
[Bandpass - 650-660 nm (brightness and pB); Resolution - 7.5 arcsec/pixel; FOV
- 1.3-4.0 R (full revolution; Sun centred); Nominal cadence 20 s (3 images/min
in different polarisation angles)]
Ø
Required
(yes/no)
Yes
Ø
Image cadence? Few minutes
Ø
FOV (full or partial
field (define area and pointing))
Full
Ø
Other
details
Possibility to trigger high cadence CME mode for passage of ejecta
through COR1 and COR2?
COR2:
[Bandpass - 650-750 nm (brightness and pB); Resolution - 15 arcsec/pixel; FOV -
2-15 R (full revolution; Sun centred); Nominal cadence 100
s]
Ø
Required (yes/no)
Yes
Ø
Image cadence? Few minutes
Ø
FOV (full or partial
field (define area and pointing))
Full
Ø
Other
details
HI1: [Bandpass - 650-750 nm (brightness); Resolution - 35
arcsec/pixel;
FOV - 20o circle centred at 13.28o to Sun centre
(3.28-23.28o along ecliptic); Nominal cadence 1
hr]
Ø
Required
(yes/no) yes
Ø
Image cadence? 10's of minutes
Ø
FOV (full or partial
field (define area and pointing))
Full
Ø
Other
details
HI2: [Bandpass - 400-1000 nm (brightness); Resolution - 240
arcsec/pixel;
FOV - 70o circle centred at 53.36o to Sun centre
(18.36-88.36o along ecliptic); Nominal cadence 3
hr]
Ø
Required
(yes/no) Yes
Ø
Image cadence? 10's of minutes
Ø
FOV (full or partial
field (define area and pointing))
Other details
Other Spacecraft/Instruments Required (give details of
observation)?
In-situ measurements of the magnetic field are required for the
helicity computation. In-situ particle fluxes are needed to look for signatures
of field lines which remain attached to the Sun. This will help to obtain a
good understanding of the CME structure and also give an indication of the
upper limit of the CME length to complement the model. Radius of interplanetary
CME also needs to be found from the in-situ data to complement that predicted
from the CME model.
Other relevant details?
Special Operational/Software Requirements? (i.e. requirements to feed
into operations planning and software during mission
development)
Ability to automatically change cadence of observations upon CME
detection?
Observation Title: CME onset
Name: Sarah Matthews
Institute: MSSL
E-mail: sam@mssl.ucl.ac.uk
Version Date: 31 May 2002
Brief Scientific Objective and Observation Overview: While on-disk
signatures in association with CME onset are now often observed in the X-ray
and EUV, the actual trigger for these events remains elusive. The 3-D view from
STEREO will provide a much less ambiguous view of pre-CME structures in the
corona, which combined with magnetic field information from Solar-B and STEREO
should provide clues to this process.
EUVI: [Bands
- He II 304, Fe IX 171, Fe XII 195, Fe XV 284 Å; Resolution - 1.6 arcsec/pixel;
FOV - 0.9 deg Sun-centred; Nominal cadence 30 s]
Ø
Required (yes/no)
Yes
Ø
Which bands?
All
Ø
Image cadence?
30s
Ø
FOV (full Sun,
partial Sun (define area and pointing)) Full
Ø
Other
details
COR1:
[Bandpass - 650-660 nm (brightness and pB); Resolution - 7.5 arcsec/pixel; FOV
- 1.3-4.0 R (full revolution; Sun centred); Nominal cadence 20 s (3 images/min
in different polarisation angles)]
Ø
Required (yes/no)
Yes
Ø
Image cadence?
Nominal
Ø
FOV (full or partial
field (define area and pointing)) Full
Ø
Other
details
COR2:
[Bandpass
- 650-750 nm (brightness and pB); Resolution - 15 arcsec/pixel; FOV - 2-15 R
(full revolution; Sun centred); Nominal cadence 100 s]
Ø
Required (yes/no)
Yes
Ø
Image cadence?
Nominal
Ø
FOV (full or partial
field (define area and pointing)) Full
Ø
Other
details
HI1: [Bandpass - 650-750 nm (brightness); Resolution - 35
arcsec/pixel;
FOV - 20o circle centred at 13.28o to Sun centre
(3.28-23.28o along ecliptic); Nominal cadence 1
hr]
Ø
Required (yes/no)
No
Ø
Image
cadence?
Ø
FOV (full or partial
field (define area and pointing))
Ø
Other
details
HI2: [Bandpass - 400-1000 nm (brightness); Resolution - 240
arcsec/pixel;
FOV - 70o circle centred at 53.36o to Sun centre
(18.36-88.36o along ecliptic); Nominal cadence 3
hr]
Ø
Required (yes/no)
No
Ø
Image
cadence?
Ø
FOV (full or partial
field (define area and pointing))
Other details
Other Spacecraft/Instruments Required (give details of
observation)?
Solar - B : SOT, XRT and EIS to provide high resolution magnetic
field, high cadence EUV/X-ray imaging and spectroscopic measurements of plasma
parameters e.g. velocity. Since EIS and SOT are not full Sun instruments
pointing would have to be defined in this case, in which a partial field could
also be used in SECCHI. Sacrificing the spectral observations and using
SOHO-MDI would give a whole Sun view and greater probability of observing the
region where onset occurs.
Other relevant details?
Special Operational/Software Requirements? (i.e. requirements to feed
into operations planning and software during mission development) This one
really needs to be done early in the mission to make use of the complementary
information from Solar-B. A co-ordinated campaign tracking an active region
during its disk passage with both STEREO and Solar-B would be the ideal
case.
Observation Title: Relationship between CMEs and magnetic
clouds
Name: Sarah Matthews
Institute: MSSL
E-mail: sam@mssl.ucl.ac.uk
Version Date: 31 May 2002
Brief Scientific Objective and Observation
Overview:
While magnetic clouds are known to have a high probability of
producing enhanced geomagnetic activity only ~ 1/3 of CMEs can be confidently
associated with magnetic clouds. In order to assess the potential
geo-effectiveness of a CME it is thus important to assess whether there are
particular characteristics that lead to the production of a magnetic cloud. The
observation would involve combining all of the SECCHI instruments with in-situ
measurements from other IMPACT and ACE to ensure a complete description of the
CME
parameters and their evolution.
EUVI: [Bands
- He II 304, Fe IX 171, Fe XII 195, Fe XV 284 Å; Resolution - 1.6 arcsec/pixel;
FOV - 0.9 deg Sun-centred; Nominal cadence 30 s]
Ø
Required (yes/no)
Yes
Ø
Which bands? Fe XII
195, He II 304
Ø
Image cadence?
30s
Ø
FOV (full Sun,
partial Sun (define area and pointing)) Full Sun
Ø
Other details Fe XII
and He II should give a good indication of the initial field configuration of
the CME site and also onset time information to compare with coronagraph
signatures.
COR1:
[Bandpass - 650-660 nm (brightness and pB); Resolution - 7.5 arcsec/pixel; FOV
- 1.3-4.0 R (full revolution; Sun centred); Nominal cadence 20 s (3 images/min
in different polarisation angles)]
Ø
Required (yes/no)
Yes
Ø
Image cadence?
Nominal
Ø
FOV (full or partial
field (define area and pointing)) Full
Ø
Other
details
COR2:
[Bandpass - 650-750 nm (brightness and pB); Resolution - 15 arcsec/pixel; FOV -
2-15 R (full revolution; Sun centred); Nominal cadence 100
s]
Ø
Required (yes/no)
Yes
Ø
Image cadence?
Nominal
Ø
FOV (full or partial
field (define area and pointing)) Full
Ø
Other
details
HI1: [Bandpass - 650-750 nm (brightness); Resolution - 35
arcsec/pixel;
FOV - 20o circle centred at 13.28o to Sun centre
(3.28-23.28o along ecliptic); Nominal cadence 1
hr]
Ø
Required (yes/no)
Yes
Ø
Image cadence?
Nominal
Ø
FOV (full or partial
field (define area and pointing)) Full
Ø
Other
details
HI2: [Bandpass - 400-1000 nm (brightness); Resolution - 240
arcsec/pixel;
FOV - 70o circle centred at 53.36o to Sun centre
(18.36-88.36o along ecliptic); Nominal cadence 3
hr]
Ø
Required (yes/no)
Yes
Ø
Image cadence?
2hr
Ø
FOV (full or partial
field (define area and pointing)) Ideally a partial field from the Sun-ward
side of the Earth to provide better cadence for slower
CMEs.
Other details
Other Spacecraft/Instruments Required (give details of
observation)?
IMPACT - magnetic field, speed profile, electron and proton
temperatures.
Similar from ACE.
Other relevant details?
Special Operational/Software Requirements? (i.e. requirements to feed
into operations planning and software during mission development) Since we
would like to determine whether specific CME parameters are more likely to
produce magnetic clouds than others it is important to be able to study CMEs
with a range of speeds. Therefore being able to vary the cadence in HI-2 would
be extremely useful to provide good coverage of the slow ones.
Observation Title: Particle acceleration at CME
shocks
Name: Sarah Matthews
Institute: MSSL
E-mail: sam@mssl.ucl.ac.uk
Version Date: 31 May 2002
Brief Scientific Objective and Observation Overview: SEP events are
now thought to fall into 2 classes: impulsive and gradual. Impulsive events are
thought to be flare-related, while the gradual events are thought to CME
driven. However, the distinction is not always a clear one and hybrid events
are often seen. The prolonged decay of the gradual events is also not well
understood. The combination of 3-D coronagraph and in-situ observations from
STEREO can be used to address these hybrid events and the role of particle
acceleration at the CME shock.
EUVI: [Bands
- He II 304, Fe IX 171, Fe XII 195, Fe XV 284 Å; Resolution - 1.6 arcsec/pixel;
FOV - 0.9 deg Sun-centred; Nominal cadence 30 s]
Ø
Required (yes/no)
Yes
Ø
Which bands? Fe XII
195, Fe XV 284
Ø
Image cadence?
Nominal
Ø
FOV (full Sun,
partial Sun (define area and pointing)) Full sun
Ø
Other details EUVI
will provide information on the CME onset and any associated flaring activity
that would accelerate particles.
COR1:
[Bandpass - 650-660 nm (brightness and pB); Resolution - 7.5 arcsec/pixel; FOV
- 1.3-4.0 R (full revolution; Sun centred); Nominal cadence 20 s (3 images/min
in different polarisation angles)]
Ø
Required (yes/no)
Yes
Ø
Image cadence?
Nominal
Ø
FOV (full or partial
field (define area and pointing)) Full
Ø
Other
details
COR2:
[Bandpass - 650-750 nm (brightness and pB); Resolution - 15 arcsec/pixel; FOV -
2-15 R (full revolution; Sun centred); Nominal cadence 100
s]
Ø
Required (yes/no)
Yes
Ø
Image cadence?
Nominal
Ø
FOV (full or partial
field (define area and pointing)) Full
Ø
Other
details
HI1: [Bandpass - 650-750 nm (brightness); Resolution - 35
arcsec/pixel;
FOV - 20o circle centred at 13.28o to Sun centre
(3.28-23.28o along ecliptic); Nominal cadence 1
hr]
Ø
Required (yes/no)
Yes
Ø
Image cadence?
Nominal
Ø
FOV (full or partial
field (define area and pointing)) Full
Ø
Other
details
HI2: [Bandpass - 400-1000 nm (brightness); Resolution - 240
arcsec/pixel;
FOV - 70o circle centred at 53.36o to Sun centre
(18.36-88.36o along ecliptic); Nominal cadence 3
hr]
Ø
Required (yes/no)
Yes
Ø
Image cadence? <
2hr
Ø
FOV (full or partial
field (define area and pointing)) Partial, sun-ward side
Other details
Other Spacecraft/Instruments Required (give details of
observation)?
IMPACT - shock speed, magnetic field, particle
flux/distribution
RHESSI - Flare -related particle information
ACE - similar to IMPACT at 1AU
Other relevant details?
Special Operational/Software Requirements? (i.e. requirements to feed
into operations planning and software during mission
development)
Although slower CMEs are less likely to drive shocks it would still be
useful to have as many images as possible in the HI-2 as the CME propagates to
help determine whether it undergoes any acceleration/deceleration, so variable
cadence and partial FOV would be useful here.
Observation Title: Synoptic CME Programme
Name: Richard A.
Harrison
Institute:
RAL
E-mail:
r.harrison@rl.ac.uk
Version Date: 6 June 2002
Brief Scientific Objective and Observation
Overview:
One of the major objectives of the STEREO effort is the routine
monitoring and identification of CMEs which are Earth-directed. Thus, we
require a standard synoptic observation programme, which is described
here.
EUVI: [Bands
- He II 304, Fe IX 171, Fe XII 195, Fe XV 284 Å; Resolution - 1.6 arcsec/pixel;
FOV - 0.9 deg Sun-centred; Nominal cadence 30 s]
Ø
Required (yes/no)
Yes
Ø
Which bands? All
Ø
Image cadence?
20 min
Ø
FOV (full Sun,
partial Sun (define area and pointing))
Full
field
Ø
Other details
Standard
synoptic cadence
COR1:
[Bandpass - 650-660 nm (brightness and pB); Resolution - 7.5 arcsec/pixel; FOV
- 1.3-4.0 R (full revolution; Sun centred); Nominal cadence 20 s (3 images/min
in different polarisation angles)]
Ø
Required (yes/no)
Yes
Ø
Image cadence?
8 min
Ø
FOV (full or partial
field (define area and pointing)) Full
field
Ø
Other details
Standard
synoptic cadence
COR2:
[Bandpass
- 650-750 nm (brightness and pB); Resolution - 15 arcsec/pixel; FOV - 2-15 R
(full revolution; Sun centred); Nominal cadence 100 s]
Ø
Required (yes/no)
Yes
Ø
Image cadence?
20 min
Ø
FOV (full or partial
field (define area and pointing)) Full
field
Ø
Other details
Standard
synoptic cadence
HI1: [Bandpass - 650-750 nm (brightness); Resolution - 35
arcsec/pixel;
FOV - 20o circle centred at 13.28o to Sun centre
(3.28-23.28o along ecliptic); Nominal cadence 1
hr]
Ø
Required (yes/no)
Yes
Ø
Image cadence?
1 hour
Ø
FOV (full or partial
field (define area and pointing)) Full
field
Ø
Other details
Standard
synoptic cadence
HI2: [Bandpass - 400-1000 nm (brightness); Resolution - 240
arcsec/pixel;
FOV - 70o circle centred at 53.36o to Sun centre
(18.36-88.36o along ecliptic); Nominal cadence 3
hr]
Ø
Required (yes/no)
Yes
Ø
Image cadence?
2 hours
Ø
FOV (full or partial
field (define area and pointing)) Full
field
Other details Standard synoptic
cadence
Other Spacecraft/Instruments Required (give details of
observation)?
Standard monitoring of
STEREO particle, field and radio data would be advantageous as would coincident
space weather monitoring programmes. Little planning is required as these would
be standard operations.
Other relevant details?
None
Special Operational/Software Requirements? (i.e. requirements to feed
into operations planning and software during mission
development)
None
In principle the range of
exposure times is limited only by the requirement that the on-board processor
times the exposure. The instrument tick is planned to be 10-15ms, thus a 100 ms
exposure will have an associated error of this order. In reality the exposure time
is limited by the requirement for good signal to noise with minimum cosmic ray hits.
Since there is no shutter
it should be borne in mind that the time taken to clock out the CCD
(2048ms for line transfers) means that the final measured
intensity will include a contribution from every pixel in the CCD
column.
The factors which limit
the instrument cadence include telemetry restrictions, cosmic ray scrubbing,
CCD readout times etc. Methods that might be used to improve the cadence
include using smaller FOVs and telemetry re-distribution - e.g. it is possible
to have continuous coverage in HI1 with no HI2 coverage and vice versa. Partial
FOVs are also possible. The images are cleaned on-board and this cosmic ray
scrubbing is one of the main limitations as far as cadence is concerned,
without additional CPU power on-board. It may be possible to consider the
option of disabling this feature where very high cadence observations are
required and cleaning cosmic rays on the ground.
Several studies require
cadences that are higher than the nominal values in HI1 and HI2. In these cases
we might consider the options listed above for improvements to the nominal
value.
Other suggestions might include on-board differencing. Pixel summing is
available on-board, both on-chip and in software - could we consider
transmitting image differences, or would the additional processing cancel out
any gains made in down-linking the data?
There will be a limited command uplink and so very complicated daily
schedules which involve several different observations requiring different
variations on any of the above methods to improve cadence, will be difficult to
execute. We might want to consider, in agreement with the rest of the SECCHI
team, the possibility of campaigns which last for as long as a few days in
order to address specific science objectives that have requirements outside of
the nominal instrument parameters. This would lead to a much simpler
schedule.
Other planning issues to consider are co-ordinations with other
instruments, both in space and on the ground. Those studies which rely heavily
on complementary data-sets from remote-sensing instruments will be most easily
achieved early in the mission when the spacecraft separation is small.