The compression rate of on board EIS data may vary depending on a few factors such as the observing target (QS, AR, CH, etc), slit/slot selection, exposures, etc.

The purpose of this study is trying to investigate how different compression schemes effect EIS data volume on board and work out a better estimation of compression rate for compression scheme (eg. DPCM, JPEG98, JPEG95, etc.)

The approach:

1. to get actual data volume from MDP status information: the inclined curve means data packets from EIS on MDP, the vertical curve means data packets dumped to ground station. So in general, known a raster's start and end time can calculate actual data volume, and then compare it with the designed data volume of this raster to get data compression rate.

2. to get related information from planning database/eis catalogue/fits header, for example: raster ID, compression scheme, designed data volume, SCI_OBJ, TARGET, slit/slot, exposures, etc.

3. prepare plots based on various factor combinations: compression rate vs. slit/slot, rate vs. target, rate vs. exposures

Some preliminary results (plots):

(The investigation here is for dates between 2007-Sep-15 and 2007-Dec-15, as EIS is operationally stable over this duration.)

• DPCM
• Second Tab
• Third Tab

QS QS,DC QS,SYN QS,CH QS,NET QS,DC,XBP QS,SYN,DC QS,DC,SEI QS,PCH

XBP,QS

AR AR,LMB AR,EFR AR,PLG AR,CH AR,NFL AR,CH,LMB

SYN SYN,DC SYN,QS,DC

PCH PCH,LMB,JET PCH,JET

JET,LMB,PCH

LMB LMB,LO LMB,PCH,SPI LMB,SPI

ENG,LMB,JET,PCH ENG,QS,DC

SYN,DC,QS SYN,DC

CH CH,JET CH,XBP CH,DC CH,LMB CH,QS CH,XBP,JET,EFR CH,BP,JET

PR PR,LMB PP,PCH

SPI,LMB

EFR SEI,EFR

DC DC,LMB WAV NET

SPI SPI,CH

BP,CH,JET BP,JET

FIL,PR FIL,QS