Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5661 Report Date: 18-Jul-95:17:49 Version: ********** Check-in Date: ********** 1.Proposal Title: FUV SPECTROSCOPY OF IOS SO2 ATMOSPHERE AND SURFACE CYCLE 4 CARRYOVER OF PROGRAMS 3862 AND 4600 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID SOLAR SYSTEM GO/CAR Sub Category ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Dr. John T. Clarke UNIVERSITY OF MICHIGAN USA 313-747-3540 ------------------------------------------------------------------------------------ 7. Abstract ------------------------------------------------------------------------------------ 8. Scientific Key Words: PLANETARY SATELLITE, PLASMA TORUS ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 0 par: 0 10. Num targs pri: 0 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: HRS FOS ------------------------------------------------------------------------------------ 12. Special sched req: Time Critical obs. ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5661 PI: Dr. John T. Clarke Proposal Title: FUV SPECTROSCOPY OF IOS SO2 ATMOSPHERE AND SURFACE CYCLE 4 CARRYOVER OF PROGRAMS 3862 AND 4600 ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Pi John T. Clarke 2660 USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. This proposal is a group of high priority cycle 2 and 3 obs.'s of Io that either were never scheduled or were not correct, and have been approved for cycle 4 by the HOPR process. ------------------------------------------------------------------------------------ 11. Address Information Name: JOHN T. CLARKE Category: PI Institution: UNIVERSITY OF MICHIGAN Address: AOSS DEPT. City: ANN ARBOR State: MI Zip Code: 481092143 Country: USA Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST b)Solar System Targets ID = 5661 [ 3] ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: IO-ACQ-SHADOW ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: OFFSET CALLISTO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD = JUPITER | STD = CALLISTO | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ REF | DATA | COMMENTS | | 1 |SURF(V) = 5.5 +/- 0.5 | ACQUISITION OF IO WHILE IN SHADOW 2 |SIZE = 2.0 +/- .2 | FOR SPECTRA IN SHADOW. STRATEGY IS 3 |SURF-CONT(2700) = 2 +/- 1 E-13 | TO ACQUIRE J2 OR J3 AND THEN BLIND | | OFFSET TO IO, BOTH IN 4.3 ARC SEC | | APERTURE. | ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 | TARGET NAME: IO-EGRESS ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE IO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD = JUPITER | STD = IO | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | OLG OF JUPITER BETWEEN 240 290, | ECL U OF IO BY JUPITER, | SEP OF EUROPA IO FROM EARTH GT 10", | SEP OF GANYMEDE IO FROM EARTH GT 10", | SEP OF CALLISTO IO FROM EARTH GT 10" | ------------------------------------------------------------------------------------------------------------------------------------ REF | DATA | COMMENTS | | 1 |SURF(V) = 5.8 +/- 0.5 | OBSERVE IO COMING OUT OF ECLIPSE 2 |SIZE = 1.0 +/- .2 | BEHIND JUPITER; BEGIN SPECTRA 10-15 3 |SURF-CONT(2700) = 2 +/- 1 E-13 | MINUTES BEFORE IO ECLIPSE | | REAPPEARANCE AND SCHEDULE WHEN | | ORBITAL LONGITUDE OF JUPITER IS 240 | | TO 290 DEGREES. PLEASE NOTE THAT THE | | WINDOWS CAN BE EXPANDED IF NEEDED TO | | SCHEDULE. | ------------------------------------------------------------------------------------------------------------------------------------ TARGET LIST b)Solar System Targets ID = 5661 [ 4] ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 3 | TARGET NAME: IO-ACQ ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE IO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD = JUPITER | STD = IO | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | SEP OF EUROPA IO FROM EARTH GT 10", | SEP OF GANYMEDE IO FROM EARTH GT 10", | SEP OF CALLISTO IO FROM EARTH GT 10" | ------------------------------------------------------------------------------------------------------------------------------------ REF | DATA | COMMENTS | | 1 |SURF(V) = 5.0 +/- 0.5 | IO ACQUISITION FOR SPECTRA OR POST- 2 |SIZE = 1.0 +/- .2 | OBSERVATION POINTING INFO. WITH IO 3 |SURF-CONT(2700) = 2 +/- 1 E-13 | IN SUNLIGHT. | ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 4 | TARGET NAME: IO-W-DARK ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE IO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD = JUPITER | STD = IO | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | TYPE = CARTO, | SEP OF EUROPA IO FROM EARTH GT 10", LONG = 288.0, | SEP OF GANYMEDE IO FROM EARTH GT 10", LAT = -15.0 | SEP OF CALLISTO IO FROM EARTH GT 10", | OLG OF IO BETWEEN 265 295, | OLG OF JUPITER BETWEEN 300 60 | ------------------------------------------------------------------------------------------------------------------------------------ REF | DATA | COMMENTS | | 1 |SURF(V) = 5.0 +/- 0.5 | OBSERVE DARK REGION ON IO WHEN IO IS 2 |SIZE = 1.0 +/- .2 | FROM ABOUT -5 TO +25 DEGREES FROM 3 |SURF-CONT(2700) = 2 +/- 1 E-13 | WESTERN ELONGATION, WHEN JUPITER IS 4 |SURF-CONT(1900) = 1.5 +/- 1 E-15 | WITHIN 60 DEGREES OF OPPOSITION. | | PLEASE NOTE THAT THE WINDOWS CAN BE | | EXPANDED IF NEEDED TO SCHEDULE. | ------------------------------------------------------------------------------------------------------------------------------------ TARGET LIST b)Solar System Targets ID = 5661 [ 5] ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 5 | TARGET NAME: IO-W-LOKI ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE IO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD = JUPITER | STD = IO | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | TYPE = CARTO, | SEP OF EUROPA IO FROM EARTH GT 10", LONG = 304.0, | SEP OF GANYMEDE IO FROM EARTH GT 10", LAT = +20.0 | SEP OF CALLISTO IO FROM EARTH GT 10", | OLG OF IO BETWEEN 280 325, | OLG OF JUPITER BETWEEN 300 60 | ------------------------------------------------------------------------------------------------------------------------------------ REF | DATA | COMMENTS | | 1 |SURF(V) = 5.0 +/- 0.5 | OBSERVE LOKI VOLCANO ON IO WHEN IO 2 |SIZE = 1.0 +/- .2 | IS FROM ABOUT +10 TO +55 DEGREES 3 |SURF-CONT(2700) = 2 +/- 1 E-13 | FROM WESTERN ELONGATION, WHEN 4 |SURF-CONT(1900) = 1.5 +/- 1 E-15 | JUPITER IS WITHIN 60 DEGREES OF | | OPPOSITION. PLEASE NOTE THAT THE | | WINDOWS CAN BE EXPANDED IF NEEDED TO | | SCHEDULE. | ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 6 | TARGET NAME: IO-W-SCAN ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE IO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD = JUPITER | STD = IO | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | SEP OF EUROPA IO FROM EARTH GT 10", | SEP OF GANYMEDE IO FROM EARTH GT 10", | SEP OF CALLISTO IO FROM EARTH GT 10", | OLG OF IO BETWEEN 250 290, | OLG OF JUPITER BETWEEN 300 60 | ------------------------------------------------------------------------------------------------------------------------------------ REF | DATA | COMMENTS | | 1 |SURF(V) = 5.0 +/- 0.5 | OBSERVE IO WITHIN +/- 20 DEGREES OF 2 |SIZE = 1.0 +/- .2 | WESTERN ELONGATION WHEN JUPITER IS 3 |SURF-CONT(2700) = 2 +/- 1 E-13 | WITHIN 60 DEGREES OF OPPOSITION. 4 |SURF-CONT(1900) = 1.5 +/- 1 E-15 | PLEASE NOTE THAT THE WINDOWS CAN BE | | EXPANDED IF NEEDED TO SCHEDULE. | ------------------------------------------------------------------------------------------------------------------------------------ TARGET LIST b)Solar System Targets ID = 5661 [ 6] ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 11 | TARGET NAME: EUROPA-ACQ ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: OFFSET EUROPA ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD = JUPITER | STD = EUROPA | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ REF | DATA | COMMENTS | | 1 |SURF(V) = 5.5 +/- 0.5 | ACQUISITION OF IO WHILE IN SHADOW 2 |SIZE = 2.0 +/- .2 | FOR SPECTRA IN SHADOW. STRATEGY IS 3 |SURF-CONT(2700) = 2 +/- 1 E-13 | TO ACQUIRE J2 AND THEN BLIND OFFSET | | TO IO, BOTH IN 4.3 ARC SEC APERTURE. | | THIS IS AN ALTERNATE TO TARGET 1. | ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5661 [ 7] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 IO-ACQ- FOS/BL IMAGE 4.3 G270H Y-SIZE=5 1 300 S 3 1 SEQ 1-3 NOGAP SHADOW Y-SPACE=128 RT ANALYSIS FOR 2 COMB=YES CYCLE 4 / 1-19 SUB-STEP=4 decision time 1s Comments: SPECTRA OF EUROPA FOR INT. ACQ. REQUIRES REAL-TIME UPLINK FOR S /C MOTIONS IN X AND Y DURING EARTH OCCULTATION. AFTER CENTERING ON EUROPA, OFFSET TO IO, WHICH IS IN SHADOW. ------------------------------------------------------------------------------------------------------------------------------------ 2 IO-EGRESS FOS/BL RAPID 4.3 G270H STEP-PATT=DEF 1 30 M 1 1 non-int READ-TIME=60. Comments: FOS EXPOSURES OF IO: BEGIN 10- 15 MINUTES BEFORE IO REAPPEARS IN SUNLIGHT FROM ECLIPSE ------------------------------------------------------------------------------------------------------------------------------------ 3 IO-ACQ FOS/BL IMAGE 4.3 G270H Y-SIZE=5 1 300 S 3 1 Y-SPACE=128 COMB=YES SUB-STEP=4 Comments: IMAGE OF 4.3 APERTURE FOR POST- UPLINK POINTING INFORMATION, PERFORMED AFTER IO COMES BACK INTO SUNLIGHT. ------------------------------------------------------------------------------------------------------------------------------------ 4 IO-ACQ- FOS/BL IMAGE 4.3 G270H Y-SIZE=5 1 300 S 3 1 SEQ 4-6 NOGAP SHADOW Y-SPACE=128 RT ANALYSIS FOR 5 COMB=YES decision time 1s SUB-STEP=4 Comments: SPECTRA OF EUROPA FOR INT. ACQ. REQUIRES REAL-TIME UPLINK FOR S /C MOTIONS IN X AND Y DURING EARTH OCCULTATION. AFTER CENTERING ON EUROPA, OFFSET TO IO, WHICH IS IN SHADOW. ------------------------------------------------------------------------------------------------------------------------------------ 5 IO-EGRESS FOS/BL RAPID 4.3 G190H STEP-PATT=DEF 1 30 M 1 1 non-int READ-TIME=60. Comments: FOS EXPOSURES OF IO: BEGIN 10- 15 MINUTES BEFORE IO REAPPEARS IN SUNLIGHT FROM ECLIPSE. ------------------------------------------------------------------------------------------------------------------------------------ 6 IO-ACQ FOS/BL IMAGE 4.3 G270H Y-SIZE=5 1 300 S 3 1 Y-SPACE=128 COMB=YES SUB-STEP=4 Comments: IMAGE OF 4.3 APERTURE FOR POST- UPLINK POINTING INFORMATION, PERFORMED WHEN IO IS IN SUNLIGHT. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5661 [ 8] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 7 IO-ACQ FOS/BL IMAGE 4.3 G270H Y-SIZE=5 1 300 S 3 1 SEQ 7-12 NOGAP Y-SPACE=128 INT ACQ FOR 8 COMB=YES decision time 1s SUB-STEP=4 Comments: SPECTRA OF IO FOR INTERACTIVE ACQUISITION: REQUIRES REAL-TIME UPLINK FOR S/C MOTIONS IN X AND Y DURING EARTH OCCULTATION. ------------------------------------------------------------------------------------------------------------------------------------ 8 IO-ACQ FOS/BL IMAGE 4.3 G270H Y-SIZE=5 1 300 S 3 1 Y-SPACE=128 COMB=YES SUB-STEP=4 Comments: IMAGE OF 4.3 APERTURE FOR POST- UPLINK POINTING INFORMATION. NEXT, OFFSET TO 0.3 APERTURE FOR SPECTRA IN LINENUM 9. ------------------------------------------------------------------------------------------------------------------------------------ 9 IO-W-DARK FOS/BL ACCUM 0.3 G270H STEP- 1 10 M 3 1 PATT=SINGLE Comments: G270H SPECTRA OF DARK SPOT ON IO AT LONG,LAT = 288,-15. ------------------------------------------------------------------------------------------------------------------------------------ 10 IO-W-DARK FOS/BL ACCUM 0.3 G190H STEP- 1 30.5 M 4 1 PATT=SINGLE Comments: G190H SPECTRA OF DARK SPOT ON IO AT LONG,LAT = 288,-15. ------------------------------------------------------------------------------------------------------------------------------------ 11 IO-W-LOKI FOS/BL ACCUM 0.3 G270H STEP- 1 10 M 3 1 PATT=SINGLE Comments: G270H SPECTRA OF LOKI VOLCANO ON IO AT LONG,LAT = 304,+20. ------------------------------------------------------------------------------------------------------------------------------------ 12 IO-W-LOKI FOS/BL ACCUM 0.3 G190H STEP- 1 36 M 4 1 PATT=SINGLE Comments: G190H SPECTRA OF LOKI VOLCANO ON IO AT LONG,LAT = 304,+20. ------------------------------------------------------------------------------------------------------------------------------------ 13 IO-ACQ FOS/BL IMAGE 4.3 G270H Y-SIZE=5 1 300 S 3 1 SEQ 13-15 NOGAP Y-SPACE=128 INT ACQ FOR 14 COMB=YES SUB-STEP=4 Comments: SPECTRA OF IO FOR INTERACTIVE ACQUISITION: REQUIRES REAL-TIME UPLINK FOR S/C MOTIONS IN X AND Y DURING EARTH OCCULTATION. NEXT, OFFSET TO 0.3 APERTURE FOR SPECTRA IN LINENUM 14. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5661 [ 9] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 14 IO-W-SCAN FOS/BL RAPID 0.3 G270H STEP- 1 24 M 3 1 SPATIAL SCAN PATT=SINGLE REQ UPLINK COMB=YES READ-TIME=60.0 Comments: VERY SLOW SPATIAL SCAN N/S ACROSS DISK OF IO. REQUIRES REVIEW BY STSCI. ------------------------------------------------------------------------------------------------------------------------------------ 15 IO-ACQ FOS/BL IMAGE 4.3 G270H Y-SIZE=5 1 300 S 3 1 Y-SPACE=128 COMB=YES SUB-STEP=4 Comments: IMAGE OF 4.3 APERTURE FOR POST- UPLINK POINTING INFORMATION. ------------------------------------------------------------------------------------------------------------------------------------ 16 IO-ACQ- HRS ACQ 2.0 MIRROR-N2 1 10S 3 1 SEQ 16-19 NOGAP SHADOW ONBOARD ACQ FOR 18 Comments: ACQUISITION OF EUROPA OR GANYMEDE FOR OFFSET TO IO IN SHADOW. ------------------------------------------------------------------------------------------------------------------------------------ 17 IO-ACQ- HRS ACQ/ 2.0 MIRROR-N2 1 18.4S 1 1 ONBOARD ACQ FOR 18 SHADOW PEAKUP Comments: PEAKUP BEFORE OFFSET: AFTER CENTERING ON GANYMEDE OR EUROPA , OFFSET TO IO, WHICH IS IN SHADOW. ------------------------------------------------------------------------------------------------------------------------------------ 18 IO-EGRESS HRS RAPID 2.0 G140L 1370. SAMPLE- 1 25M 1 1 non-int TIME=12.75 Comments: G140L SPECTRA OF IO: BEGIN 15 MINUTES BEFORE IO REAPPEARS IN SUNLIGHT FROM ECLIPSE. SCHEDULE IN DARK TIME DUE TO 1304 OXYGEN AIRGLOW. ------------------------------------------------------------------------------------------------------------------------------------ 19 IO-ACQ HRS IMAGE 2.0 MIRROR-N2 1 96.8S 3 1 Comments: IMAGE OF IO IN LSA AFTER SPECTRA. I ESTIMATE 100 COUNTS /DWELL POINT FROM IO DISK IN SUNLIGHT. ------------------------------------------------------------------------------------------------------------------------------------ Scan Paramters Form Proposal ID: 5661 [ 10] ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 1 Exposure Logsheet lines: 14.00 FGS Scan: CONTINUOUS Dwell Only: dwell points/line: 0 Seconds per dwell: 0.00 Scan width (arc-secs): 0.0000 Scan length (arc-secs): 1.2600 Angle between sides (degrees) 90.00 Number of lines: 1 Scan rate (arc-sec/sec): 0.0009 PA of first scan line (degrees) 25.000 Scan frame (CEL or S/C): CEL Length Offset (arc-sec): 0.6300 Width Offset (arc-sec): 0.0000 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5661 [ 11] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE RAPID ACCUM ACQ ACQ/PEAKUP ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters Y-SIZE Y-SPACE COMB SUB-STEP STEP-PATT=DEF READ-TIME=60. STEP-PATT=SINGLE READ-TIME=60.0 SAMPLE-TIME ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO/CAR ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category SOLAR SYSTEM ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SEQ 1-3 NOGAP; RT ANALYSIS FOR 2; CYCLE 4 / 1-19; decision time 1s; non-int; SEQ 4-6 NOGAP; RT ANALYSIS FOR 5; SEQ 7-12 NOGAP; INT ACQ FOR 8; SEQ 13-15 NOGAP; INT ACQ FOR 14 SPATIAL SCAN; REQ UPLINK SEQ 16-19 NOGAP; ONBOARD ACQ FOR 18 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G270H G190H MIRROR-N2 G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names IO-ACQ-SHADOW IO-EGRESS IO-ACQ IO-W-DARK IO-W-LOKI IO-W-SCAN EUROPA-ACQ ------------------------------------------------------------------------------------------------------------------------------------