13716( 4) - 18-May-2015 16:02:06 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 13716 Version: 4 Check-in Time: 18-May-2015 16:02:06 STScI Edit Number: 1 Title Constraining the history of the outer Solar System: Definitive proof with HST ------------------------------------------------------------------------------------ Type Cycle GO 22 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. David E. Trilling Northern Arizona University Y CoI: Dr. William M. Grundy Lowell Observatory N CoI: Dr. Paulo Fernando Penteado Northern Arizona University N CoI: Prof. Hilke E. Schlichting Massachusetts Institute of Technology N CoI: Dr. Cesar I. Fuentes Universidad de Chile N CoI: Dr. Ruth A. Murray-Clay Smithsonian Institution Astrophysical N Observatory CoI: Dr. Keith S. Noll NASA Goddard Space Flight Center N CoI: Dr. Susan D. Benecchi Planetary Science Institute N CoI: Dr. David Nesvorny Southwest Research Institute N ------------------------------------------------------------------------------------ Abstract We propose to image five faint cold classical Kuiper Belt Objects (KBOs) to test hypotheses about the collisional evolution of the outer Solar System. There is an observed break in the size distribution of cold classical KBOs at around 40 km. If small cold classicals exhibit bluer colors and a smaller binary fraction than large cold classicals then the nature of the break is collisional. If the small cold classicals are as red as their larger counterparts and have a similar binary fraction, then the break is most likely primordial and a product of the environment in which these objects formed. Our data in-hand suggests the collisional model, using both binary statistics and color measurements, but the signal is not unequivocal. We propose to observe the five smallest available cold classical KBOs to search for binaries and measure colors. The five KBOs that we will observe here, combined with our existing data, will allow us to determine conclusively the physical process that drive the break in the size distribution and the evolution of the outer Solar System. This well-posed experiment will offer for the first time a direct observational test of the broad collisional history of the outer Solar System and is only possible with HST. ------------------------------------------------------------------------------------ Observations Description ------------------------ This project aims to image five faint Cold Classical Kuiper belt objects to obtain their colors and to see if they are binaries. Observations consist of 4 F606W frames and 4 F814W frames, but with the 4 F814W frames inserted into the middle of the F606W frames to minimize potential lightcurve effects on the colors. In each of the two filters, we do a standard box dither, but since the F606W observations are divided in time, this is accomplished by means of a pair of line dithers, offset from one another via POSTARG offsets. This is the same observing strategy as was used successfully in program 13404. ------------------------------------------------------------------------------------ 13716( 4) - 18-May-2015 16:02:06 - [ 2] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: 2000-PM30 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: ASTEROID transneptunian object ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=ASTEROID, A=44.180962830000, E=0.053161090000, I=2.278460000000, O=129.77317000000, W=66.0206700000, M=115.185580000, EQUINOX=J2000, EPOCH=21-JUL-1999, EpochTimeScale=UTC ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 24.6 +/- 0.5 Ephemeris Center: EARTH ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 TARGET NAME: 2000-FC8 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: ASTEROID transneptunian object ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=ASTEROID, A=44.0935530334332, E=0.05994109059962618, I=0.7119090149437264, O=332.4115354730703, W=29.83588670051765, M=201.4990485058602, EQUINOX=J2000, EPOCH=09-DEC-2014, EpochTimeScale=UTC ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 24.8 +/- 0.5 Ephemeris Center: EARTH ------------------------------------------------------------------------------------------------------------------------------------ 13716( 4) - 18-May-2015 16:02:06 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 3 TARGET NAME: 2000-PN30 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: ASTEROID transneptunian object ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=ASTEROID, A=45.0465308200, E=0.1073728200, I=1.512680000, O=16.043320000, W=277.158460000, M=17.884550000, EQUINOX=J2000, EPOCH=11-JUL-1999, EpochTimeScale=UTC ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 24.3 +/- 0.5 Ephemeris Center: EARTH ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 4 TARGET NAME: 2000-OB51 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: ASTEROID transneptunian object ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=ASTEROID, A=37.994847660000, E=0.0398840300, I=4.4533400000, O=126.853230000, W=208.318470000, M=340.265980000, EQUINOX=J2000, EPOCH=11-JUL-1999, EpochTimeScale=UTC ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 23.8 +/- 0.5 Ephemeris Center: EARTH ------------------------------------------------------------------------------------------------------------------------------------ 13716( 4) - 18-May-2015 16:02:06 - [ 4] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 5 TARGET NAME: 2011-JX31 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: ASTEROID transneptunian object ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=ASTEROID, A=44.9307361900, E=0.108133680000, I=3.3065300, O=139.160670000000, W=19.450190000000, M=106.399370000000, EQUINOX=J2000, EPOCH=19-APR-2011, EpochTimeScale=UTC ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 24.9 +/- 0.5 Ephemeris Center: EARTH ------------------------------------------------------------------------------------------------------------------------------------ 13716( 4) - 18-May-2015 16:02:06 - [ 5] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.145 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 13716( 4) - 18-May-2015 16:02:06 - [ 6] Visit: 01 Visit Requirements: SCHED 30% On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 2000-PM30 WFC3/UVI ACCUM UVIS2-C51 F606W CR-SPLIT=NO 1 170 S (340 POS TARG -.1582, S 2C-SUB S) 0.0289867; PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 2000-PM30 WFC3/UVI ACCUM UVIS2-C51 F814W CR-SPLIT=NO 1 365 S (730 POS TARG -0.153256, S 2C-SUB S) -0.144537; PATTERN 1 2 ------------------------------------------------------------------------------------------------------------------------------------ 3 2000-PM30 WFC3/UVI ACCUM UVIS2-C51 F814W CR-SPLIT=NO 1 365 S (730 POS TARG 0.0541835, S 2C-SUB S) 0.0385166; PATTERN 1 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 2000-PM30 WFC3/UVI ACCUM UVIS2-C51 F606W CR-SPLIT=NO 1 170 S (340 POS TARG 0.0494375, S 2C-SUB S) -0.145331; PATTERN 1 4 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ 2000-PM30 1 WFC3/UVI ACCUM UVIS2-C5 F606W 1 none none none 1 N/A S 12C-SUB 2000-PM30 1 WFC3/UVI ACCUM UVIS2-C5 F606W 2 none none none 1 N/A S 12C-SUB 2000-PM30 2 WFC3/UVI ACCUM UVIS2-C5 F814W 1 none none none 1 N/A S 12C-SUB 2000-PM30 2 WFC3/UVI ACCUM UVIS2-C5 F814W 2 none none none 1 N/A S 12C-SUB 2000-PM30 3 WFC3/UVI ACCUM UVIS2-C5 F814W 1 none none none 1 N/A S 12C-SUB 2000-PM30 3 WFC3/UVI ACCUM UVIS2-C5 F814W 2 none none none 1 N/A S 12C-SUB 2000-PM30 4 WFC3/UVI ACCUM UVIS2-C5 F606W 1 none none none 1 N/A S 12C-SUB 2000-PM30 4 WFC3/UVI ACCUM UVIS2-C5 F606W 2 none none none 1 N/A S 12C-SUB 13716( 4) - 18-May-2015 16:02:06 - [ 7] Visit: 02 Visit Requirements: SCHED 30%; BETWEEN 01-MAY-2015:00:00:00 AND 31-JUL-2015:23:59:00 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 2000-FC8 WFC3/UVI ACCUM UVIS2-C51 F606W CR-SPLIT=NO 1 170 S (340 POS TARG -.1582, S 2C-SUB S) 0.0289867; PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 2000-FC8 WFC3/UVI ACCUM UVIS2-C51 F814W CR-SPLIT=NO 1 365 S (730 POS TARG -0.153256, S 2C-SUB S) -0.144537; PATTERN 1 2 ------------------------------------------------------------------------------------------------------------------------------------ 3 2000-FC8 WFC3/UVI ACCUM UVIS2-C51 F814W CR-SPLIT=NO 1 365 S (730 POS TARG 0.0541835, S 2C-SUB S) 0.0385166; PATTERN 1 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 2000-FC8 WFC3/UVI ACCUM UVIS2-C51 F606W CR-SPLIT=NO 1 170 S (340 POS TARG 0.0494375, S 2C-SUB S) -0.145331; PATTERN 1 4 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ 2000-FC8 1 WFC3/UVI ACCUM UVIS2-C5 F606W 1 none none none 1 N/A S 12C-SUB 2000-FC8 1 WFC3/UVI ACCUM UVIS2-C5 F606W 2 none none none 1 N/A S 12C-SUB 2000-FC8 2 WFC3/UVI ACCUM UVIS2-C5 F814W 1 none none none 1 N/A S 12C-SUB 2000-FC8 2 WFC3/UVI ACCUM UVIS2-C5 F814W 2 none none none 1 N/A S 12C-SUB 2000-FC8 3 WFC3/UVI ACCUM UVIS2-C5 F814W 1 none none none 1 N/A S 12C-SUB 2000-FC8 3 WFC3/UVI ACCUM UVIS2-C5 F814W 2 none none none 1 N/A S 12C-SUB 2000-FC8 4 WFC3/UVI ACCUM UVIS2-C5 F606W 1 none none none 1 N/A S 12C-SUB 2000-FC8 4 WFC3/UVI ACCUM UVIS2-C5 F606W 2 none none none 1 N/A S 12C-SUB 13716( 4) - 18-May-2015 16:02:06 - [ 8] Visit: 03 Visit Requirements: SCHED 30% On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 2000-PN30 WFC3/UVI ACCUM UVIS2-C51 F606W CR-SPLIT=NO 1 170 S (340 POS TARG -.1582, S 2C-SUB S) 0.0289867; PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 2000-PN30 WFC3/UVI ACCUM UVIS2-C51 F814W CR-SPLIT=NO 1 365 S (730 POS TARG -0.153256, S 2C-SUB S) -0.144537; PATTERN 1 2 ------------------------------------------------------------------------------------------------------------------------------------ 3 2000-PN30 WFC3/UVI ACCUM UVIS2-C51 F814W CR-SPLIT=NO 1 365 S (730 POS TARG 0.0541835, S 2C-SUB S) 0.0385166; PATTERN 1 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 2000-PN30 WFC3/UVI ACCUM UVIS2-C51 F606W CR-SPLIT=NO 1 170 S (340 POS TARG 0.0494375, S 2C-SUB S) -0.145331; PATTERN 1 4 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ 2000-PN30 1 WFC3/UVI ACCUM UVIS2-C5 F606W 1 none none none 1 N/A S 12C-SUB 2000-PN30 1 WFC3/UVI ACCUM UVIS2-C5 F606W 2 none none none 1 N/A S 12C-SUB 2000-PN30 2 WFC3/UVI ACCUM UVIS2-C5 F814W 1 none none none 1 N/A S 12C-SUB 2000-PN30 2 WFC3/UVI ACCUM UVIS2-C5 F814W 2 none none none 1 N/A S 12C-SUB 2000-PN30 3 WFC3/UVI ACCUM UVIS2-C5 F814W 1 none none none 1 N/A S 12C-SUB 2000-PN30 3 WFC3/UVI ACCUM UVIS2-C5 F814W 2 none none none 1 N/A S 12C-SUB 2000-PN30 4 WFC3/UVI ACCUM UVIS2-C5 F606W 1 none none none 1 N/A S 12C-SUB 2000-PN30 4 WFC3/UVI ACCUM UVIS2-C5 F606W 2 none none none 1 N/A S 12C-SUB 13716( 4) - 18-May-2015 16:02:06 - [ 9] Visit: 04 Visit Requirements: SCHED 30% On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 2000-OB51 WFC3/UVI ACCUM UVIS2-C51 F606W CR-SPLIT=NO 1 170 S (340 POS TARG -.1582, S 2C-SUB S) 0.0289867; PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 2000-OB51 WFC3/UVI ACCUM UVIS2-C51 F814W CR-SPLIT=NO 1 365 S (730 POS TARG -0.153256, S 2C-SUB S) -0.144537; PATTERN 1 2 ------------------------------------------------------------------------------------------------------------------------------------ 3 2000-OB51 WFC3/UVI ACCUM UVIS2-C51 F814W CR-SPLIT=NO 1 365 S (730 POS TARG 0.0541835, S 2C-SUB S) 0.0385166; PATTERN 1 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 2000-OB51 WFC3/UVI ACCUM UVIS2-C51 F606W CR-SPLIT=NO 1 170 S (340 POS TARG 0.0494375, S 2C-SUB S) -0.145331; PATTERN 1 4 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ 2000-OB51 1 WFC3/UVI ACCUM UVIS2-C5 F606W 1 none none none 1 N/A S 12C-SUB 2000-OB51 1 WFC3/UVI ACCUM UVIS2-C5 F606W 2 none none none 1 N/A S 12C-SUB 2000-OB51 2 WFC3/UVI ACCUM UVIS2-C5 F814W 1 none none none 1 N/A S 12C-SUB 2000-OB51 2 WFC3/UVI ACCUM UVIS2-C5 F814W 2 none none none 1 N/A S 12C-SUB 2000-OB51 3 WFC3/UVI ACCUM UVIS2-C5 F814W 1 none none none 1 N/A S 12C-SUB 2000-OB51 3 WFC3/UVI ACCUM UVIS2-C5 F814W 2 none none none 1 N/A S 12C-SUB 2000-OB51 4 WFC3/UVI ACCUM UVIS2-C5 F606W 1 none none none 1 N/A S 12C-SUB 2000-OB51 4 WFC3/UVI ACCUM UVIS2-C5 F606W 2 none none none 1 N/A S 12C-SUB 13716( 4) - 18-May-2015 16:02:06 - [ 10] Visit: 05 Visit Requirements: SCHED 30% On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 2011-JX31 WFC3/UVI ACCUM UVIS2-C51 F606W CR-SPLIT=NO 1 170 S (340 POS TARG -.1582, S 2C-SUB S) 0.0289867; PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 2011-JX31 WFC3/UVI ACCUM UVIS2-C51 F814W CR-SPLIT=NO 1 365 S (730 POS TARG -0.153256, S 2C-SUB S) -0.144537; PATTERN 1 2 ------------------------------------------------------------------------------------------------------------------------------------ 3 2011-JX31 WFC3/UVI ACCUM UVIS2-C51 F814W CR-SPLIT=NO 1 365 S (730 POS TARG 0.0541835, S 2C-SUB S) 0.0385166; PATTERN 1 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 2011-JX31 WFC3/UVI ACCUM UVIS2-C51 F606W CR-SPLIT=NO 1 170 S (340 POS TARG 0.0494375, S 2C-SUB S) -0.145331; PATTERN 1 4 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ 2011-JX31 1 WFC3/UVI ACCUM UVIS2-C5 F606W 1 none none none 1 N/A S 12C-SUB 2011-JX31 1 WFC3/UVI ACCUM UVIS2-C5 F606W 2 none none none 1 N/A S 12C-SUB 2011-JX31 2 WFC3/UVI ACCUM UVIS2-C5 F814W 1 none none none 1 N/A S 12C-SUB 2011-JX31 2 WFC3/UVI ACCUM UVIS2-C5 F814W 2 none none none 1 N/A S 12C-SUB 2011-JX31 3 WFC3/UVI ACCUM UVIS2-C5 F814W 1 none none none 1 N/A S 12C-SUB 2011-JX31 3 WFC3/UVI ACCUM UVIS2-C5 F814W 2 none none none 1 N/A S 12C-SUB 2011-JX31 4 WFC3/UVI ACCUM UVIS2-C5 F606W 1 none none none 1 N/A S 12C-SUB 2011-JX31 4 WFC3/UVI ACCUM UVIS2-C5 F606W 2 none none none 1 N/A S 12C-SUB 13716( 4) - 18-May-2015 16:02:06 - [ 11] Summary Form for Proposal 13716 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2-C512C-SUB ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 01-MAY-2015:00:00:00 AND 31-JUL-2015:23:59:00, PATTERN 1 1, PATTERN 1 2, PATTERN 1 3, PATTERN 1 4, POS TARG -.1582, 0.0289867, POS TARG -0.153256, -0.144537, POS TARG 0.0494375, -0.145331, POS TARG 0.0541835, 0.0385166, SCHED 30% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names 2000-FC8, 2000-OB51, 2000-PM30, 2000-PN30, 2011-JX31 ------------------------------------------------------------------------------------------------------------------------------------