Solar-C Plan-B mission

System requirements on
ultra-high data rate telemetry andscientific operations
2008.11.20

T. Shimizu and K. Matsuzaki(ISAS/JAXA)
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Scientific requirements to be considered indesigning the telemetry and operation
related system
The following top-level requirements shall beconsidered in the system design.
1. Continuous observations as long as possible
2. High-speed telemetry rate for plan-B telescopes
3. Scientific operations can be conducted like groundbased telescopes

Each topics will be discussed in next pages.

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21. Continuous observations• A “sun-synchronous” polar orbit has provided
continuous viewing of the Sun for 9 months of ayears.
– “Hinode” takes this orbit.

• Geo-synchronous or equivalent orbit is anothercandidate.
– SDO will take this orbit.
– Eclipse seasons for 1-1.5 months, once per day.

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32. High speed telemetry required••

A 0-th order estimate on the amount of data outputs from onboard
telescopes by Dr. Katsukawa
One of key scientific capabilities is to acquire spectro-scopic orspectro-polarimetric data with highest possible cadence. Thisrequirement requires high speed telemetry capability.

Raw data (pixel/sec)
Compressed (bits/sec)

Visible-UV Telescope

EUV Spectrometer

Average obs.

Burst obs.

Averageobs.

Burst obs.

1.8M

18M

102K

1M

9.4M
0.5M here)(assumed
5-7bits/pixel 94M
lossless compression

5M• Will expect data flow with rate smaller than 10Mbps for average observations• Will need the capability for performing burst observations by the Visible-UV
telescope, which is expected to produce ~100Mbps data flow.
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4Visible-UV Telescope Data Estimate• Average observations
ExamplesSlit polarimetric obs, high S/N, low rate

Imaging obs, low rate2048(spatial)x256(λ)x4(pol.)2048x2048 at 4λ

10 sec for one position

10 sec for one set

Raw data flow

2048x256x4/10= 0.2M pix/s (3.2Mbps)

2048x2048x4/10= 1.6M pix/s (41Mbps)

Compression

Lossless, 7bits/pix

Lossy, 2bits/pix

Lossless, 5bits/pix

Lossy, 2bits/pix

1.4Mbps

0.4Mbps

8.0Mbps

3.2Mbps

Image productsCadence

Data flow• Burst observations
ExamplesImage productsCadence
Raw data flow
Compression
Data flow

Slit polarimetric obs, low S/N, high rate

Imaging obs, high rate2048(spatial)x256(λ)x4(pol.)4096x4096 at 10λ (1A/100mA)

1 sec for one position

10 sec for one set

2048x256x4/1= 2M pix/s (32Mbps)

4096x4096x10/10= 16M pix/s (256Mbps)

Lossless, 7bits/pix

Lossy, 2bits/pix

Lossless, 5bits/pix

Lossy, 2bits/pix

14Mbps

4Mbps

80Mbps

32MbpsSolar-C SDM

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EUV Spectrometer Data Estimate
ExamplesSlit spectroscopic obs
high S/N, low rate

Slit spectroscopic obs
low S/N, high rate

Image products

2048(spatial)x512(λ)

2048(spatial)x512(λ)	

Cadence10 sec for one position

1 sec for one position

2048x512/10= 0.1M pix/s (1.2Mbps)

2048x512/1= 1M pix/s (12Mbps)

Raw data flow
Compression
Data flow

Lossless, 5bits/pix

Lossy, 2bits/pix

Lossless, 5bits/pix

Lossy, 2bits/pix

0.5Mbps

0.2Mbps

5Mbps

2Mbps

This 0-th estimate is a good start point for plan B mission?

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3. Onboard data processing (1/2)• Image compression is probably required on board.
• For the visible-UV telescope, 18M pixel/s raw data flow
may be converted to 94Mbps or less compressed dataflow.
• A deep consideration will be needed to realize the realtime (JPEG) compression on board.
– Assuming that a compression scheme needs 10 operations per
1 pixel, the CPU with 100MIPS performance can process in thereal time the data flow with up to 10M pixel/sec. This means afaster processor or a hardwire consideration will be required.

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3. Onboard data processing (2/2)• Space Wire will be the standard I/F line between
components in the ISAS future satellites.
– The first ISAS satellite with Space Wire I/F isBepiColombo MMO. The current performance in thelaboratory is 50~100Mbps.
– With a multiple number of lines in parallel, the data
speed can be increased to a multiple of 50~100Mbps.
– The transfer of ~18M pixel/s raw data and ~100 Mbps
compressed data would have reality with Space Wire.
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4. Orbit and Communication Band (1/3)• Sun-synchronous polar vs. Geo-synchronous as candidate• Sun-synchronous polar orbit– Short duration (~10 min) at each station contact.
– Need a large number of station contacts and high telemetry downlink
speed• ~100Mbps is required when 15 contacts per day (150min in total).
• This speed allows to perform observations with ~10Mbps on average.

– K-band needs to be explored for high speed downlink.
• X-band usage has ~10Mbps upper limit (SFCG recommendation)
because 100Mbps transfer occupies wide (greater than 10MHz)
bandwidth.
• New area for JAXA and need new ground station facilities• K-band is not yet used at Svalbard, although a future plan exists.
• Ka (37-38GH) communication is easily affected by weather condition(rain falls), giving complicated operation.
• Deep negotiation will be needed for frequency allocation.
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4. Orbit and Communication Band (2/3)• Geo-synchronous orbit– Continuous communication link with the spacecraft for 24 hours, if a
dedicated antenna is newly prepared.
– With the 24hr continuous downlink, X-band is a strong candidate.
• X-band downlink is ~10Mbps upper limit (SFCG recommendation)• If higher speed is really required from science, we also need to explore
K-band usage (Ku-band?), which is a new area for ISAS and needs anew ground facility.

– A dedicated antenna is required.
• Only for downlink purpose?
Cheap. USC and JAXA NGN antenna are used for uplink.
• Should also have uplink capability? Expensive

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4. Orbit and Communication Band (3/3)• S-band can be used for commanding and housekeeping
telemetry.
– New S-band transponder will be available with 256Kbps uplink
and up to 2Mbps downlink for Astro-H and ISAS satellites.

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5. Operate like ground-based telescopes (1/5)• Hinode’s scientific operation planning– Observations including observing sequence and pointing
schedule are planned in the previous day of the commanduplinks.
– Minor pointing adjustment may be made 7~8 hours before thestart of the OP timeline.

• It is difficult to take quick actions for capturing activities
and dynamical changes always occuring on the Sun.
• For the plan B mission, one of key scientific observations
is spectro-scopic or spectro-polarimetric observations.
– Scanning with a narrow slit takes a fairly long duration to cover awide field of view, although high throughput telescopes will beconsidered.
– Good capturing the events of interest with spectroscopic
observations would much increase scientific returns.
– Good capturing is extremely important for studying dynamics andactivities on the Sun.
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5. Operate like ground-based telescopes (2/5)• Autonomous functions for capturing small activities, suchas flux emergence, are not easily designed.
– Most reliable method is that scientists in the operation room
select the observing target, by real-time monitoring some latest
images from the telescope.

• Such an environment should be prepared for the plan B.
– 10~15 min timescale may be a good design target.
• The selection of target (pointing change) can be made 10~15 min
before the start of an observation.
• 10~15 min is the typical timescale of flux emergence.

– Components needed to realize the environment.
• Some latest images from the telescope can be displayed on amonitor in the operation room.
• A user-friendly and easy capability for selecting the target.
• A capability for generating and verifying the uplink commands.
• Uplink connection for commanding to the telescope.
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5. Operate like ground-based telescopes (3/5)• Continuous downlink and uplink connection with thesatellite on a geo-synchronous orbit is preferable fordesigning the environment.
• 24 hours connection may increase scientists working
load and we may need an operation rule for performing
real-time target selection.
• The ground support system needs to be well designed,
so that it can provide more simple and easy planning.
– Significant efforts should be given to the ground support system.

• Each telescope may need a capability to take different
telescope pointing, because of simple observation
coordination.
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5. Operate like ground-based telescopes (4/5)• No intelligent functions for performing observations may
not be needed on board.
– Hinode has Mission Data Processor (MDP), which provides
observation tables with too intelligent functions for SOT andXRT.
– The MDP observation tables look too complicated because ofproviding a large amount of freedom on observations.
– The table function on board should be much simplified, or it may
be partially located on the ground support system.

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5. Operate like ground-based telescopes (5/5)• Bus functions available in the ISAS future
missions will be effectively utilized in the detaileddesign.
– Commanding functions• A new “timeline” function, i.e., the list of command and UTtime, which is different from OP/OG.
• Command uplink speed will be significantly increased from4Kbps to 256Kbps.
• No memory dump is required for table memory upload.
Instead, check-sum can be used for upload verification.

– Quick-look data downlink (for sun-synchronous orbit)• Only two partitions are available in the Hinode’s DR.
• A large number of DR partitions can be defined in DR. This
capability may be useful to downlink the latest data withhighest priority.
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Summary
1.

A geo-synchronous or equivalent orbit is more
preferable for plan B, rather than a sun-synchronouspolar orbit.
With a geo-synchronous orbit, ~10Mbps continuous
downlink in X-band can be a candidate.

2.
–3.

If sciences require very long continuous data flow with higher
than10Mbps, we should explore K-band downlink.

High-speed telemetry rate for telescopes–4.

<10Mbps for average and possible ~100Mbps burst obs

We should have capabilities to perform scientificoperations like ground-based telescopes.
-Quick selection of observing target
Easy and simple planning of observations
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