AIDJEX Bulletin #40 - Polar Science Center - University of Washington

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t@ the spacecraft during each orbit. The spacecraft memory can be used as an extended buoy memory to permit the integration of multiple one-minute samples into ten-minute averages. i .-.e treatmcrit of each data reception at the spacecraft as independent allows the use of multiplc addresses and higher than nominal transmit duty cycles to obtain increased da ta capacity ..?Ti ::-. no increase in equipment costs. The availability of up to 13 sntelljte passes per dav in i)b-:z~ regions means that up to 4000 bits per day can be transmitted for each address. There is trade-off between the nrimber of data bits and level of redundancy required, and the nu::ber PI satellite passes available and number of addresses used for each platform. This trade-cif I :- a function of latitude, and with the number of passes available in polar regions we hi17.e h extremely conservative with respect to data redundancy in our system designs. This should ch2:;e as we become more confident of system performance. Flexibility in position accuracy requires that measurements made in the satellite have sufficient accuracy potential for the most demanding users. To achieve refraction-limited posit accuracy of 200 meters, a Doppler system like RAYS needs measurement accuracy of 0.1 Hz and 0.61 seconds, an order of magnitude better than RA". The use of multiple addresses offers the possibility of increasing the amount of data used in the position computation, as a way :f improving fix accuracy. The flexibility offered to the user by random access data collecticx and positioning systems should be retained and enhanced in the future. 7. Real-Time Data Readout Option The Ni.mbus spacecraft transmits all data in real time in addition to storing these data on rzznetic tape. When the spacecraft is critiiin view the data can be receivedwit'nportable equip.-::t and, with the proper formats, can be decoded and interpreted essentially the instant they arc transmitted from the platform. The most obvious use of this capability for data buoy work is to provide for inmediate verification of platform performance during checkout of electrcnics. This is the only practical method of authoritative confirmation of buoy pcrfor;nance in remozt areas. The same capability could be used to obtain data for forecasting without waiting for process5r;g by NASA. The primary purpose of this real-time data transmission is to provide a backup data collect mode in case of tape recorder failure in the spacecraft. The spacecraft must be in view of both the platforms and the data retrieval site for sufficient time to recover the desired dzr3, Thus, the data retrieval site should be in the vicinity of the platforms, which is of specic: significance to experiments in remote areas where NASA does not maintain facilities. The us? of buoys in the Southern Ocean might be one experiment which would benefit from a direct re;;- QUt capability in the Antarctic in the event of a tape recorder failure. An important addition to the real-time data transmission of the spacecraft would be the predicted orbit parameters and measured satellite clock and orbit errors needed for position fi-: computation. This would permit fix computation by users and wou1.d make possible dispersing the data processing function around the globe to areas where the data are being collected ar-i used. 8. Conclusion The data buoy program associated with AIDJEX has been large and diverse enoughtogainanapprsciation for the many practical difficulties involved in developing and using several kinds CT data buoys. Time seems to have been the ingredient in shortest supply, and should t?,ereforn be canserved in future work. The money spent (about $2 million dollars including logistics costs), while not extravagant, must certainly be considered adequate for the objectives, whi:i were fairly well sati.sfied. Personal initiative was important, and more of this ingredient would have improved the results. We have been fortunate to try many new things with very few failures, but this should not bs interpreted as an endorsement of the policy of trying something new when a proven method car. be made to work. The only good pressure sensor is a used one. This is a good philosophy frz buoys as well, althoush one probably has to settle for used designs and long checkout tests since hardware recovery is difficult. The RAMS has 2 to 6 kilometer position accuracy and is probably capable of 500 meters. By taking full advantage of the flexibility available through random access, a data capacity of one to several thousand bits per platform per day can be acheived. There are real benefits 10 be achieved through real-time readout of data from the spacecraft. These proven captbilities of FUtIS, plus the potential ready to be realized, make it highly desirable that a new I 10
deployment of the RAMS be scheduled so that the system can be utilized through the rest of :his decade. A new orbit complementary in time to the existing one would be desirable. Data collection and tracking from orbiting spacecraft is in its infancy. By comparison the Navy Navigation Satellite System (Transit) has been an operational system for 14 years, and currently consists of six Satellites which provide users with a completely self-contained pcsitioning capability. The insight gained in the use of this system has lead to a new satellite system which will provide continuous position information to a few meters, from a constellarion of up to 24 satellites. The message is not that we need 24 data collection satellites. Ths current concept of data collection and tracking is elegant in its simplicity. The challeng-. is to raise our level of sophisitication in using the data collection and tracking concept tohigher levels where even greater benefits will be realized. 9. Acknowledgments This work was supported by the National Science Foundation, the Office of Naval Research, the National Oceanic and Atmospheric Administration, the Bureau of Land Management, the Canadiaii Polar Continental Shelf Project, and the National Aeronautics and Space Administration. We wish to thank the staffs of the Nimbus Operations Center, Goddard Space Flight Center; Polar Research Laboratory, Santa Barbara; the Applied Physics Laboratory, University of Washingtoz, and our colleagues at AIDJEX. 10. References [l] N. UNTERSTEINER, AIDJEX Bulletin 26 [2] P. MARTIN, in: Means of Acquisition and Communication of Ocean Data, WMO No. 350, 1973. [3] D. P. HAUGEN and K. M. DOZIER, Applied Physics Laboratory, University of Washington, APL-UW 7422 (1975). [4] W. P. BROWN, AIDJEX Bulletin 22 (1973). (1974). [5] W. P. BROWN and E. G. KERUT, Ocean 75, IEEE Publication 75 CHO 995-1OEC (1975). [6] S. P. BURKE and B. M. BUCK, Ocean 75, IEEE Publication 75 CHO 995-1 OEC (1975). [7] P. MARTIN, Ocean 74, IEEE Publication 74 CHO 873-0 OCC (1974). [8] Nimbus F TWERLE Doppler Data Processing, General Electric, Space Division No. 72SD4257 (1972). [9] T. GREEN, Geoscience Electronics, GE-13, No. 1 (1975). [lo] A. S. THORNDIKE, AIDJEX Bulletin 24 (1974). 11
Page 2 and 3: DATA BUOYS AIDJEX BULLETIN No. 40 J
Page 4 and 5: NOTE TO FRIENDS, AND BYSTANDERS . .
Page 6 and 7: SUMMARY OF TECHNICAL DEVELOPMENTS I
Page 8 and 9: milestones, kept the vendor working
Page 10 and 11: The scene during deployment of HF-N
Page 12 and 13: The initial AIDJEX scientific plan
Page 14 and 15: poizr-orbiting satellite, which is
Page 18 and 19: BUOY NAHE COMMUN. COMMANDS FIXES TA
Page 20 and 21: L( 0 I 2 3 4 3 Radial error, kilome
Page 22 and 23: The buoy will be subjected to tempe
Page 24 and 25: nics occupy about 12 feet of the 17
Page 26 and 27: Ill -- - KEY AIUJEX WIN WW AEBa 0 4
Page 28 and 29: event that a melt pond should form
Page 30 and 31: chute supplied by Paranetics Inc. i
Page 32 and 33: 6'" IqORGANIC LITHIUM BP.TTEI?Y IMP
Page 34 and 35: OM (AD RAMS) UREMEN~ \ AIRDROP N m
Page 36 and 37: provides a grid from which geostrop
Page 38 and 39: words; a four-bit air temperature w
Page 40 and 41: PERFORMANCE OF MET/OCEAN BUOYS IN A
Page 42 and 43: Sensor samples were taken every thr
Page 44 and 45: strengths are known, were used with
Page 46 and 47: the ice (causing reduced shear). An
Page 48 and 49: (McPhee, Mangum, and Martin) , TABL
Page 50 and 51: 70°N 75'N n 3 P 17OOW (D Y 170°W
Page 52 and 53: 12OOW * U Station 25. Xeasurements
Page 54 and 55: (McPhee , Mangum, and Martin) 2701
Page 56 and 57: (McPhee, Mangum, and Martin) a 0 a
Page 58 and 59: "i BUOY 4 I 43 360- 309- 257 206 15
Page 60 and 61: a30gl 251 I 60 511 r 43 BUOY 4 I
Page 62 and 63: n 4, (McPhee, Mangum, and Martin) 8
Page 64 and 65: (McPhee, Mangum, and Martin) 33 W c
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. '-,..I.. . B A R R O W W I N D S
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:
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I 25 23 t h--:!li[ NCI PiHCEl4l 22
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.5 .4 .3 0 A R 2 R 0 W J - 0 B U -
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9 1.5 1.0 c 8 w .5 R 930 $ 565 1000
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Clock corrections were applied rout
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Q) u o z z i 4- 4- Z + + z f n 9 Ef
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TABLE 1 DIFFERENCES IN DAILY TEMPER
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Laboratory calibration of the ADRAM
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3.20- - 1 t W o? 2 3.051 ...:-.;..
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POSITION MEASUREMENTS OF AIDJEX MAN
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some redundancy. Four points were u
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75.5 75.: - E75.1 LLI % y75.c - 1 1
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The translocation principle removes
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POSITION ACCURACY To evaluate the q
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TABLE 1 STAND-ALONE ACCURACY 68th P
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Az i mu t h s When both receivers a
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DATA PROCESSING Following the field
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model ice motion in the statistical
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FREC 1 INCY / DOPPLER / FREQUENCY /
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35 30 25 v) > 0 2 20 LL 0 r= E m 15
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An example of a large-scale buoy ar
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observations are needed in remote a
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useful for determining how various
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as well as velocity fields, we must
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Since small changes in the yield su
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The transformation of the system of
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e able to judge how well such a mod
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then the flow rule becomes Q = +A -
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[-B' -F Finally, we eliminate Carte
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differential equation. 2. Discontin
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Substituting (36) and (37) into (34
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arbitrarily assign the values of 1
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The special case when advection can
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TABLE 1 STRETCHING, STRESS, ASP CHA
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ate of deformation, we have normali
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CHARACTERISTIC EQUATIONS The ordina
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One way to circumvent the problems
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The equations governing solutions a
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It is readily seen that when body f
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which may be substituted into equat
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a the stress derivative dCldS remai
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Although we have not studied in thi
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Courant, R., and D. Hilbert. 1962.
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A RESEARCH PLAN TO TEST THE AIDJEX
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the barges managed to reach their d
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APPROACH A baseline simulation 0-f
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SENSITIVITY OF ICE RESPONSE TO DIFF
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Since free drift of ice is computed
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and what is observed becomes less i
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stresses appear to be relatively un
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ehavior is directly related to accu
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TABLE 1 COMPARISON OF ESTIMATED ERR
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a) Base line b) 24-hour prediction
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\ / a) Base line b) 24- hour predi
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a) Base line b) 24- hour predi ct i
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Page 180 and 181:
\ / a) Base line b) 24-hour predict
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.. a) Base line b) 24- hour predict
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J2 a) Base line b) 24-hour predicti
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) 24-hour prediction c) 36-hour pre
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8 Figure 17. AIDJEX surface pressur
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APPENDIX 1 AIDJEX DATA FILES 1. Pos
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9A. Surface-1 eve1 ai r pressure (d
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19. Surface pressure (Val i dated)
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APPENDIX 2 AIDJEX DATA TRANSFERRED
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I -7-71327GEO A Cards (continued) 7
Page 202:
B Cards (continued) 201
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