STScI TIPS/JIM 18 September 2008 NICMOS/NCS Anomaly and Status Anton Koekemoer 1 NICMOS/NCS Anomaly and Status Timeline overview: NICMOS/NCS was commanded

STScI TIPS/JIM18 September 2008

NICMOS/NCS Anomaly and StatusAnton Koekemoer

1

NICMOS/NCS Anomaly and Status Timeline overview:

NICMOS/NCS was commanded to shutdown on Sep 10 to prepare for NSSC-I

Subsequent recovery on Sep 11 lasted ~ 6 hours before safing 3 subsequent retries safed Safings typically indicated above-average current drawn by the circulator

motor Current status / prognosis

Possibly due to water ice/contaminant interfering with circulator pump Other anomalous telemetry confirms likelihood of contaminants No evidence of any permanent damage to the mechanical system

Plans forward Decision by HST-P to allow system to warm up, thaw contaminants Cooldown would take a few weeks, similar to SMOV3B Given SM4 October launch date, remainder of Cyc 15 & 16 NICMOS

will execute in Cycle 17



2

Initial NCC restart timeline 255/01:14:05

– Circulator On (1200 Hz) 255/01:27:37

– Compressor On (5000 Hz) 255/02:33:02

– CPL Control 255/003:07:56

– CPL Operate/Compressor Ramp (6000 Hz) 255/03:10:39

– PID Operate (7043 rps + Surge effects) 255/05:44:00

– Exit FSW-defined Surge (7330 rps) 255/07:57:47

– Safing indicating overspeed limit for Circulator pump– No apparent deviation of the Circulator differential pressure (MNCIDFPR) or

the Circulator frequency (MNCIIFRQ)



3

NCC Circulator Failure - 2008/255 History Buffer Collection

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0 50 100 150 200 250

Sample Number

Raw Counts

(52)MNCIDFPR

(54)MNTBAIPR

(62)MNCIINII

(67)MNCOIFRQ

(69)MNCORSPD

(70)MNCIRSPD

(71)MNTBASPD

(72)MNCOINOI

(201)MNCOSLIP

(202)MA3SE03

(55)MNCOCMDI

(61)MNCOINII

(53)MNCOINPR

(74)MNTBALDI

(68)MNCIIFRQ

(60)MNCIINIV

(56)MNCICMDV



4

NCC Circulator Failure - 2008/255 History Buffer Collection

0

500

1000

1500

2000

2500

3000

3500

4000

4500

185 190 195 200 205 210 215 220 225 230

Sample Number

Raw Counts

(52)MNCIDFPR

(54)MNTBAIPR

(62)MNCIINII

(67)MNCOIFRQ

(69)MNCORSPD

(70)MNCIRSPD

(71)MNTBASPD

(72)MNCOINOI

(201)MNCOSLIP

(202)MA3SE03

(55)MNCOCMDI

(61)MNCOINII

(53)MNCOINPR

(74)MNTBALDI

(68)MNCIIFRQ

(60)MNCIINIV

(56)MNCICMDV



5

2008 restart - current and pressure diff.Circ Current and DP 9/10/08 Restart

0

50

100

150

200

250

0:00:00 1:00:00 2:00:00 3:00:00 4:00:00 5:00:00 6:00:00 7:00:00 8:00:00

Current (mA)

0

0.2

0.4

0.6

0.8

1

delta-p (psid)

MNCIINII EU

MNCIDFPR EU



6

2007 restart - current and pressure diff.Circ Current and DP 1/29/07 Restart

0

20

40

60

80

100

120

01/29/07 2000 01/30/07 0000 01/30/07 0400 01/30/07 0800 01/30/07 1200 01/30/07 1600 01/30/07 2000 01/31/07 0000

Current (mA)

0

0.2

0.4

0.6

0.8

1

1.2

delta-p (psid)

MNCIINII

MNCIDFPR



7

2003 Restart - current and pressure diff.Circ Current and DP 8/7/03 Restart

0

20

40

60

80

100

120

08/07/03 1200 08/07/03 1600 08/07/03 2000 08/08/03 0000 08/08/03 0400 08/08/03 0800 08/08/03 1200

Current (mA)

0

0.2

0.4

0.6

0.8

1

1.2

delta-p (psid)

MNCIINII

MNCIDFPR



8

Differences between 2008 vs 2007/2003On-Orbit History

2002: Initial start-up after installation during SM3B 2002: NCC Restart following Turboalternator (TBA) failure in SMOV 2003: Restart following DOY 213 SEU corrupting the Circulator

commanded voltage (NCC only) 2007: Restart following 027/2007 NCC Safing event due to Total Pressure

Sensor (TPS) limit violation (NCC only) Comparison:

Absolute temperature of circulator housing and NICMOS return higher during prior restarts

dT between circulator housing and NICMOS return higher this time Circulator current higher during first hour of recent restart Circulator restart transient appears similar during initial restart but current

is 1.5X after 20 sec At circulator housing temperatures of nominally 120 K, the circulator

current was higher by 2X during recent restart Anomalous current event noted during recent restart prior to shutdown



9

Contaminant Possibilities Scenario: Ice particle is dislodged during initial cool down event.

– May be related to the short duration of the stoppage. Particle runs through circulator turbine. Higher mechanical load leads to mismatch in phase angle between back-

EMF and drive signal.– Causes large rise in Circulator current.– Slight drop in Circulator voltage consistent with large draw, and is in opposite

phase.– Current is a good indicator of motor torque.

Perturbed rotor triggers speed sensor to have additional switches per revolution, and appears as an erratic increase in speed.

Circulator does NOT drop out of sync. Creare has study on the size range

– 10 u to 1 mm size range No good theory on how ice formed Cannot be explained by change in temperature and partial pressure.



10

Subsequent restart attempts 09/14/2008 20:00

Circulator current threshold was lowered from 381 to 130 mA, to avoid running the system at high current for prolonger period of time

Safed almost immediately due to current threshold limit exceeded 09/15/2008 16:00

Circulator current threshold was raised from 130 to 150 mA Safed this time due to circulator speed violation limit exceeded

09/15/2008 20:00 Circulator speed limit threshold was raised Ran for about 20 - 25 minutes Safed due to likely current limit exceeded (telemetry was lost during the

final minutes)



11

NCC Circulator Failure on Start (DT 251) - 2008/258 (14 September 2008)History Buffer Collection

(Sensors 52 54 62 67 69 70 71 72 201 202 55 61 53 74 68 60 56 )

0

500

1000

1500

2000

2500

3000

3500

4000

4500

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45

Time (mf)

Raw Counts

(52)MNCIDFPR

(54)MNTBAIPR

(62)MNCIIN II

(67)MNCOIFRQ

(69)MNCORSPD

(70)MNCIRSPD

(71)MNTBASPD

(72)MNCOINOI

(201)MNCOSLIP

(202)MA3SE03

(55)MNCOCMDI

(61)MNCOINII

(53)MNCOINPR

(74)MNTBALDI

(68)MNCIIFRQ

(60)MNCIIN IV

(56)MNCICMDV

DT 251 Compare1 Value (MNCIINII)

Previous MNCIINII Limit = '0420'X = 1056 decNew MNCIINII Limit = '0178'X = 376 decSTB Reported Count = 395 dec (EU = 137 mA)

DT 251 Compare2 Value (MNCIIFRQ)1000 Hz Limit = '07B0'X = 1968 dec



12

NCC Circulator Failure on Start (DT 120) - 2008/259 (15 September 2008)

History Buffer Collection

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Time (mf)

Raw Counts

(52)MNCIDFPR

(54)MNTBAIPR

(62)MNCIINII

(67)MNCOIFRQ

(69)MNCORSPD

(70)MNCIRSPD

(71)MNTBASPD

(72)MNCOINOI

(201)MNCOSLIP

(202)MA3SE03

(55)MNCOCMDI

(61)MNCOINII

(53)MNCOINPR

(74)MNTBALDI

(68)MNCIIFRQ

(60)MNCIINIV

(56)MNCICMDV

DT 120 Compare2 Value (MNCIRSPD)1396.1 rps Limit = '0B10'X = 2832 dec



13

NCS System with Temperatures & Parasitics

Power ConversionElectronics andTA Load Resistors

Compressor

Cold Load Interface

Cryocooler Loop

BayonetCouplers

Flexible Metal Hoses

Main NeonFill Bottle

Neon RefillBottle

SV1 SV3

SV2

MV1

SolenoidValves

Circulator

SV4

MV2

Existing NICMOSCryostat

NICMOSCooling Loop

C irculating Loop

Capillary PumpLoop Evaporator

Heat RejectionInterface

Recuperator

Turboalternator

T1MNCOINLT

T3MNAFTCOT

T4 MNPTAILT

T6 MNPLINTTT7 MNPNCOLT

T9 MNRNCILT

TrejMNHTREEJT

FlexlineInlet 0.19 W

Outlet 0.26 W

Tested5.105 W

BayonetsIn 0.78 W

Out 1.69 W

Supp Brkt0.04 watts

Analysis1.29 W

Total6.395 W

Rigid TubesInlet 0.08 WOutlet 0.065 W

Total parasiticsexpected to

be lower at BOL



14

NICMOS Dewar with Temperatures and Parasitics

Cryo ValveHeaters (2)

TEC Radiator

Cryovalves2.22 watts

(includes htrs)

Internal0.40 watts

Load to tank0.67 watts

Review of MEB/BBpowerdown shows parasitcchange is consistentwith model predictions



15

Previous NICMOS Cool-downs

Cool–down of the NICMOS dewar (from 3 previous NCS start-ups)

Red curve = weighted average of the Ne inlet and outlet temperatures

Mar 2002SMOV3b

Aug 2003 Jan 2007



16

Current / Forward Plans NICMOS / NCS:

Continue warming up to ~270 K, enable contaminants to thaw Keep TECs running to dewar - essentially retain system in as similar state

as possible to post-cryogen / pre-SMOV3B Keep to original SM4 plan to commence cooldown after SM4

SMOV & Calibration programs: May need to defer start of NICMOS SMOV4 by a few weeks, since

cooldown would likely take longer than previously planned Likely augment NICMOS SMOV4 plan to include more comprehensive

filter wheel tests, PAM/FOM tests, focus (similar to SMOV3B) Post-SMOV4 Cycle 17 calibration may need additional observations if

there are changes in the properties of the system GO programs:

All remaining Cycle 15 and 16 programs are being retained and will execute after SMOV4 along with the Cycle 17 NICMOS program

Documents

STScI TIPS/JIM 18 September 2008 NICMOS/NCS Anomaly and Status Anton Koekemoer 1 NICMOS/NCS Anomaly and Status Timeline overview: NICMOS/NCS was commanded