A set of instruments designed to detect the occurance of electrical breakdown was flown on a synchronous-orbit satellite. The LeRC sensors were installed on cables inside the vehicle. Accordingly, they respond to signals coupled into the satellite wiring system. The SRI sensors were located on the exterior of the vehicle and detected the RF noise pulses associated with surface breakdowns. The results of the earlier SRI program are being used to design and develop a set of intrumentation suitable for inclusion as a general piggy-back package for the detection of the onset of satellite charging and breakdowns on synchronous orbit satellites

Adamo, R. C.

Nanevicz, J. E.

English

NASA Technical Reports Server

i_ _ :. i
ii
_ 1. Back_rouhd. 723
i°-'_ 2, Te_t Satellite Instrumentation 724
L, 3. Orbital Data 727
! ! 4. Scathe Transient PulSe Monitor 731i i l_eforcnees 734
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ii 2. Transient Response Measurements
on a Satellite Systemi-!
" J.E. H_eviez a'ndR.C. Adamo
_l'-i' Electr_aanetle Stleni:esLaCtate@i !, StQnfordResearchInstitute
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0_-3,.. In 1974, a set of instrurhentS designed to detect the occurrence of e_ectrical
i=)_ breakdowns was flown on a synchronouS-orbit Satellite. 1 The measurements make
i_ an interesting complen_ent to those reported earlier at this conference by Bob
_!- Lovell of NASA LeRC. The LeRC sensors were installed on cables inside the
i "°_
_=_ vehicle. 2 Accordingly, they respond to signals coupled into the satellite wiring
!_?, System, The SRI sensors Were located on the exterior of the vehicle arid detected
_ _ _r t_X_ noise pulses aSSOciated with Surface breakdowns.
i_'_ The reSultS of the earlier SiqI program a_e being used to design and develop a
_o_ set of instrumentation suitable for inclusion aS a general ptggy-back package for
i_-_'_'i_'! the detectionOf the on.etof _tt_.11itechargingand breakdowns offsynchronous orbitsat llites, This system will b_ flown as the Transient Pulse Monitor (TPM) rys-
.... ,' tern on the SCA THA spacecraft.i_ _,
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', 2. TEST StTELL|TF_IN!I;-Tfil:_IENTATION
....,_. The inStr_entatton flown on the test satellite was capable Of detecting the
onset of geomagnettcally disturbed c0ndttlons and of detect|ng and c0Unti_g electri-fy,
e&l breakdowns. 1 The system, sl_own tn Figure 1, used a sensor plate mOuhtedon the outs|de Surface of the veh_le aft both an electric dipole antenn_ tO pick up
_ noise pulses and as a Larqlmuir ion probe. Since the probe electrode waJ biased
i/. -5. i3 volts wlth respect to the vehicle frame, it normally collected positive ions
and repelled photoelectronS, Under dtstU_'be_! c0n_itio_s the ion probe system _-
_, measures the differenc_ between the photoelectron current from the Surface of the
_; detector pla_ and the plasma electron current incident on the plate. Thus, sub-
s_orms t_re tx_dtcated I_y. a depressed probe current. Since the dc ampl_ier used
with the ioh probe system was unipolar, times when the _urreut iS reversed are
indLcated.by a zero i_a probe _urrent reading.
NoiSe pulses induced in the sensor plate antenna are coupled through capscitor.
C to the preamplifier-counter electronics. Sensitivity teStS of the pulse counting
system were conducted using the set up shown in Figure 2. A thermal-control,
panel was placed inside a glails bell jar and illuminated with an electron beam .to
generate discharges from the mirror cells comprising the surface of the panel.
The sensor electrode and else;tonics System flown on the flight vehicle were used
tO dete_t the noise pUlseS generated. PrOvisiOnS Were made tO place the eens0_' at
var{ous distances from the edge of the thermal control. The reSUlts Of these tests
:_ indicated that the puise counter would reliably detect breakdowns within roughly a
_i. meter Of the sensor plate.
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',, Figures 3 and 4 show data reeord_, during both t_ndistu_bed and dtst_bed-
i_ 'i! geomagnetic field-conditions for one complete satellite orbit. At synol_r-on0us
_/
_i / altitudes, each Orbit is 24 hr lOng, sampling all local times equally. Data from
°_ the ion-Clz_'rent probe are plotted as a fut_ction of local time (LT) in the upper panel
._: of Figures 3 and 4. These data were selected.at po_.nts in the satellite rotation at
:-_. Which the tot_ probe _urrent was a maxim_ (this corresponds to the oz-ie_tation-
_ at which the detector plate is most ne_ly pel_endicdla_- to the sun directlot_ re-
:" Suiting th_ m_im_m photoemission current). The geomagnetic field conditions
:_ Were determined-by examination of-Ap andKp shown at the top of Figure-_ 3 and 4.
_:: F._.gure 3 ShOwS data typically recorded during undisturbed geomagnetic field
i_i_" conditions. It shows the dinr-,_al variation occurs because of the r_epehdence of
:_ photoelectron current on the angle between the sun direeti0n and the detector plate.
-: At local evening and local morning the sun is normally incident to the detector
plate, and the peak photoele_tr0n c_rrent-density has a maximum of about 80 ,A /
m 2. At local midnight the sun is obliquely incld_nt to the detector plate, and the
_:! peak photoelectric current has a minimum of about 30 ,A/m 2. Near local noon
--:- the body of the spacecraft Shadows the detector-, and the photoelectron current is
i:::, reduced nearly to zero, as Shown from 10.7 - 13.3 hours LT i,t Figure 3. These
_-: data _,_present the UsUal diu_'nal _rlatiOn Of peak photoelectr,)n _urrento and no
: _ d+_pressions ._f the probe Current indicating the injection Of et.ergetic electrons are
_, obsex'ved.
The pulse-counter dataAre ShOwn in the low_r pane_s of Figures $ and 4. The
i=i" data plotted at.e the number of diScharge_ per minute that are dete_ted by the pulse
counter. The.number of counts w_re collected and averaged 0V_r a 10-rain period.
.,' For Lhe quiet geomagnetic period shown inFi&-._re 3. few discharges ere detected
i i.
= .... by the instrument except from local evening to local midnight during which rates
:-_ aVerag{n_ Slightly less than l/tutti a_e observed. Count rates typically near 30/hr
_:. al'e ob_.'rved on aJmost every orbit _rom l_cal _vening to local _idnig'ht.
i -" FigUre 4 illustrates data recorded during an o_it On 31 JanUary 1974 for
_-: • which a mOdet'ate geomagnetic field distu,:bance was indicated by the magnetic
indiceS. The irijecti0_i of etierg_tic electrons a{ Synchron0US altitude was detected
by depresSionS Of the total pr6be ctirrent _used by in,Peases in th_ plasma'-elee-
_ii_ tron cUrrent during the injection event.
Two example_ of data recorded d_tring Satellite eeiipse are shOwh in FigUres
_.. a_d 6. Figttr_ 5 Show_ the ion-ct_rrent probe and p_lse counter/iOta recorded
_-,!_ during undietizrbed geOmagfletie conditi0r]S. Ddring satellite eclipse the p_bbe
:_ curPen{ from {he _etectoz _ pl_ie drops to nearly _.ero becaizse solar ultravioie{
_' r' rkdtation is hot tSre_en{ tO cdt_e_eph0t0emisS|0h from the detector p},ate.
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A# - iS _ JANUARY 11_,_L
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=_; 1sos 200o 22o0 0000 020G, 0400 0600 080C 1000 1200 1400 1600 1SO0
*"_'_', LOCAL TIME -- hnl
/::.,. LOCAL LOCAL LOCAL LOCAL LOCALEVENING MIDNIGHT MORNING NOON EV_=NIN(_
_' FigUre 3. StatlC-Charge Experiment Data From an Orbit for which No Substorm
-:_ " Activity was Obse.,",,ed. (The ion-cub'rent probe data showS the usual diurk_al
_i!,_, variation. Few electrical discharges are observed except on the interval from
o:_i local evening to lO_ai _ht, )
.... !
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100 ENERGETI(_
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..... |X 0o_-
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,5.
.);..- _0O0 200o _0o 0O0O (_00 o40o o60o 0_0 I000 _0 1400 iS00 _S00
.... LOCAL TiME _ l_ta
o°i" L0_AL L_AL L_CAL LOCAL LOCAL
:_,i I_VE_NiN(_ MIDNIGHT MORNIN(_ NOON I_VENIN_
o
....... Figure 4. _tatl_-Ch&rge Exper|m(_nt Data From an Orbit fOE'which Subst_rm
=_'_,£_ Activity' was Observed.. (Depreastonb _f th_ i_n-probe cLi_rent ne**r local mid-
_ rli._'_itare caused by _e injection O_ energetic electron_ to Sy!ichron_u_ altiti_des.
o:;ii_' Discharge rates as high _e Elk per minute are measured by th_ pulse cOUflter
o!_._ durln_ the electron InJectlbri event. )
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! _ _ATELLITE
_ _ ,J J ,J
2300 _ 0106 O_YO
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u LOCAL TIME -- hrs
FigUre 5. Static-ChargeExperiment Data Recorded During UnCtisturbedGeomag-
neticField ConditionsThrough SatelliteEclipse. (Theprobe currentdrops to
nearly zero when the photoelectric current iS cut off by the earth's shadow. Only
a few dischargesare 0bserved_luringthispass. ) ...............
i,°th
I w I_ SATELLITE
., 23_i0 0000 0100 020o
_ Or l
-0 "
8 _ _ _h_ _
LO_AL TiMg _ hra
FigUre 6. Static-Charge Exper_nefit Dat_ Recorded Durth_ DiSturbed Geomag-
rietic Field Co/ldltit)ne Tllrough Sdtelilte _clipse. (Art energetic electron itljection
, event eiriddl$chs_ rates as high d$ ten per minute _re observed dt/rtn_ this p,_ko,
: The dlschar_eiJ are associated witll the Injection event (flOte del_resBed ion probe
currentlr_therthan with dat_ilit_ecltpi_.)
|
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O0000008-TSE06
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ZJ Smooth changes in the total probe current On either sitie of Satellite eclipse are
_ caused by ehanffes in the satellite oz_ientdtioti (see Figure 3 and the related dlSC_s-
_ sion of the dtt_l_nal variation in total probe current). Only s few pulse cOtJnts are
_i ObserVed by the pulse cotmter during thls pass. (The pulse eoun'_or data are
_: accumulated af_d-_._ged Over a 2 rain pel;iOd f6r the data shown in F: -tt_#_._
=-): and (_.)
_' ' I_Igure _ shows an example Of data recorded during a magnetOspheric substorm
i_ nea_. satellite eclipse. A depression of the ion probe current indicatirig the injec-
t: '_ion of energetic electrons is ObserVed just after the satellite emerge_ from
_:_:- eclipse (compare these dat_ _ith those Shown in Fil_ure 5). DiSCharge rates as
_._'::_ highevent.as10/rain are observed in a_Sociation.with this substOrm electron-injectiot_ '1
_: The data in Figure 6 show that the_discharges are aSSociated with the injection
_i_ of the energetic electrons near local mitinight, and not _vith s_telltte eclipse. The
_- beginning of the plasma-injectiOn event shown in Figure _ canno_ be determined
._, from the ion-chrrent probe data because the Satellite is in eclipse, it is possible
_.. that the discharge rates r_ay have been enhanced during satellite eclipse; however
_- the generatin_ mechaniSn_ of the discharge,, is. clearly the energetic plasma injec-
_ tion during the magnetospheric substorm.
:_' These _Our examples of discharges observed by the static charge experiment
_} are t_pical of the several conditions under which SynchrOnoUs orbiting satellites
-_ must _unction. They ShOW that electrical discharges are Observed du¢iag sub-
_,:_ Storms at rates nea_ 10/rain on the sateUite'S e_ternal SurfaCe. These disclterges
• occur when energetic electrons are injected tO.synchronoUS altitudes near local
_i:. midnight. These discharges are probably caused by the chal_git_g of dielectric
_:_- surfaces to large negative potentials during the electron injectl0ft events.
..... Other discharges are observed near local eveflin_ and at ol'her points in Orbit
at which discharges were not expected to occur. These discharges have lower
rates (i/2 minl; hOWeVer, they occur on e#sentially all sateUite orbits from local
evening to local midnight. The generatto_ of tneae discharges iS not well under-
Stood at the tii_e of this writing, i
_everal types Of engtneerin_ orbital anbmalies have occurred off this satellite
that have Been supposed td be related to electrical dischargeS. TheSe anomalies
COnsiSt of a type of anomalous detec_o_ reBI)0rise and an m_Otftr_anded z_e@et of a
_atellite cohimand citY,nit. These an6malies have oc_urred.o_,, several other
Satellites iri _dditioft tO the satelli_,e oft which this expeti_flent was flOWfl. An
e]tamiflatioft o_ the values o_ gP_iaftd-Based geon_agnetic indices at the time_ of
occul'reflce of the aftomalies etrt_ngly suggests thai they are related to intense sub-
Atorrh activity. Thus, it _a_ _ugge_ted that such &n6mkiles wes_e gefterated by
iftt_rference from _he eiectron_agftetic radiatt0n Of elec_rlcdl discharges.
O0000008-TSE07
During the period of-operatlo_ o._ tl;_,_=.xpertment, se#e=_alo_cgrrences of both
t_loes 05 these anom=lltes were reported. For the anomalous detector response, a
tOtal,of 35 occurrences were reported. For 31 of these cases a dl=chat'Be was
ObSerVed by the experiment coincidently with the anomalous detector response.
These anomalous t'esponses were reported oh seve_'al-different days, arid the proba-
bility that the coincidences occurred by chance is essentially =ero. The='e web's a
total of 6 of the uncommanded _ir_uit resets, att_i 5 o( these resets occurred
cOtnci¢lently with dete_tiOn of discharges by the experiment. Thus, data from this
experiment has confirmed the hypothesis that these types of orbital engineering
anomalies are _at_sed by interference from these electrical dischargeS.
,ma_
4. SCATilA TRANSIENTPULSE _IONITDR
Based On the experience gained in the satellite tests, a low-le_/ei progr_r_ of
planning and instrurnent development was initiated at SHI. The objective was the
development of a Set Of compact, lightweight instruments tO detect the Occurrence
of an electron injection event, to measure electric field E and current density J at
the vehicle surface, and tO detect, count, and characterize the pulse waveforms
from electrical breakdOWns on the satellite surface. A design goal was to develop
simple instruments suitable for USe on a piggy-ba_k basis oft a large ntlmber of
satellites.
The ptilSe det_ctior_ and _haracterizatiot_ System Will be repacka_ed and flown
on the SCATHA satellite as a TPM. Although the TPM system can be used to mea-
Sure pulses either 0n the outside 0r inside of the Satellite. the SCA THA TPM
system will be used entirely with internal sensOrS Since the electromagnetic signa-
ture of the breakdown pulse on the exterior o_ the vehicle Will be characterized by
the SC1-2 e_q_ertment.
The purpose of the TPM system will be to.acquire amplitude and pulse charac-
teristics of tranSientS coupled into vehicle power and signal lines when .the spate-
craft experiences arc discharges. Requirements imposed on the TPM System are
as fOllOwS:
(1) Measure pe_k pulse amplitude both + and - separately.
(_) Determine number of tranSierits absolute (+ and -).
(3I MeaSure total energyboth + and - separately.
(4) Accomplish these measurements within the following constraints:
(a) 60 dB dynamic range on ampllfiet_s.
(b) Select either a single pulse arid/Or multiple pulseS.
(c) FrequencyteSporise > 50 MHz.
These meaSt_remeflt cap_b|litlt _ are i|iuStrated graphte_Uy in Figure _.
, It i !
O0000008-TSE08
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_IN_ LI_PULSE
,I.
f i':
THRESHOLD _'_ _i
T .i
AMPLI_'UDE
° PEAK AMPLITUDE
+ _ ENERGY
- _ ENERGY
ABSOLUTENUMBER OF PULSESABOVE THI_ESHOLD
Figure 7. Data Derived From Transient-Pulge Monitor
The _nctlon,_tldeployment of tlieTPM system v_{llbe as follows:
(1) FOul" (4) separate channel_ capable of yielding the complete dtita stipulated
under requirement._ for each channel.
(2) LocatiOnS within the Spacecraft wili be:
(a) Cable bundle antenna O.ow impedance).
(b) Cable bundle antenna (high impedance).
{c) Current probe On primary power reference ground.
(d) Current probe on solar array power input.
A functional blocR diagram of the TPM is shown in Figure 8. The ultimate
form of the SyStem Stemmed from the requirement that itbe able tO provide infor-
mation about the induced noise pulses even though the parameters of interest might
vary Over a cOhSidersble range. Wide dynamic rarlge_ were achieved in SeVeral
ways. FirSt, lOgaritllmic amplifier/detector_ were used trl the pulse-peak rues-
| surin_ SyStem. The puise-integral measuring system has provisions for adjustin_
! tliPeSliold ifl orbit to a_rold the possibility of data betn_ inadVertefltly co_taminated
by sySteni noise. Siflce it is not cleaP _#hat th._ prf ot breakdown/J on SCATHA will
_: be, prOviSiOns are incl.uded to command the pulse-peak and pulse-integi-Sl.meaSur-
in_ Systems io operate with a i s_c measurin_ window or to op.er.ate for Only
:,, i00 ,See after the _irSt pulse occUPlng lfi a telemetry window,
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The sampie-and-h01d circuit for each output channel is arranged go th,t data
Obtained during One telemetry Window axe tran_fsrr-ed to the sanlple-and-hold
where they are stored for one teler_etry peniod during which time all of th_ outpt_t
• _ channels are interrogated by the telemetry #ystem. ThUs, ali of the data read
during a particular window were generated during the same Single telemetry period ..........
The pulse-peak detectors indicate the peak _mplitude observed during the
c0mmantled wtnd0_. (If several pulses occlir, the highest will be measured. )
The pulse-integral system indicAteS the inivgral over the entire window of that
signal above the-commanded thresh01d level. The _Vent-cour|ter indicates the
number of pulSeS Occuring during a 1 sec period regardless of which mode is
commanded for the pulse-peak and pulse-integral systemS.
Packas_ng of the system is such as to minimiie size and weight tn order that
it can be used as a piggy-ba_k installation with r_inlmum _eight, volume, and
power impact.
References
1. Nanevtcz, J.E., Adamo, lq. C., and Scharfman, W.E. (1974) SAtellite-Life-
_r_e Monitoring, Final Report Pz_0jeet 261 i, Contract FO470 I-71- C-01_0,
Stanford R6dearch Institute, Menlo ParlL Calif,
_. gtevens0 N.J._ L0vell, R.R., and Klinect, V.W. (1976) PreliminAry l_eport
On _,he CTS Transient Event ._.ounter Perf6rms_c.e Through the I_7_' 5prirlg
_ci!p._e.seaso'n., NASA Technical _emorsndum N_ T_ Z-7'_48_. Lewis
Research center, Cleveland, Ohio.
-_': .... _l ........


Transient response measurements on a satellite system

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