Data communication status of the ARGO floats

Hiroyuki NAKAJIMA^*1 Yasushi TAKATUKI^*2 Keisuke MIZUNO^*2 Kensuke TAKEUCHI^*3 Nobuyuki SHIKAMA^*3

Abstract

We investigate the data communication status of the ARGO floats, that deployed until February 2001 in the seas adjacent to Japan. The mean receive rate of the data via the ARGOS system, which calculated from the periods while floats flies overhead of the float, is 52%. The mean error rate of the transferred data, which detected by the CRC code in the data, is 21%. These rate varied according to the float position and the periods during the float stayed at the sea surface. East of Japan (35-40N,140-145E)was the worst 5 degrees-grid area in communication status, where the receive rate is 7% lower than the average and 3% higher than the average. The worst 6-hour period is 12:00-18:00 in JST, when the receive rate is 9% lower than the average and the error rate is 4% higher than the average. The communication status seemed to be affected by interferences of the radio were around Japan. The second-generation Argos instruments have about 10% higher receive rate than the first-generation ones, but no difference found in the error rate. Considering the orbits of the ARGOS satellites, most effective periods for data communication from the ARGOS floats in the seas adjacent to the Japan is 00:00-08:00 in JST.

Keywords : ARGO float, data communication, ARGOS system

*1 Marine Works Japan Ltd.
*2 Ocean Observational Research Department
*3 Frontier Observational Research System for Global Change

1. Introduction

2. Data communication status of the Argo floats

WMO ID	ARGOS ID	CTD sensor	Parking Depth(m)	Average time of the float staying at the sea surface(hour)	Periods of the float staying at the sea surface(JST)	Observation cycle	Repetition rate(sec)	Float deployed day(JST)
29032	28935	SBE	1500	19	17h~12h (18h~13h)	28擔	90	2000/3/22
29033	28936	SBE	1500	19	17h~12h (10h~05h)	14擔	90	2000/3/22
29034	28938	SBE	2000	21	22h~19h	10擔	90	2000/10/21
29035	28940	FSI	2000	21	22h~19h	10擔	90	2000/10/21
29042	06496	SBE	2000	8	02h~10h	10擔	44	2001/2/16
29043	06495	SBE	2000	8	06h~14h	10擔	44	2001/2/16
29044	06498	SBE	2000	8	10h~18h	10擔	44	2001/2/16
29045	06497	SBE	2000	8	12h~20h	10擔	44	2001/2/16
29046	06500	SBE	2000	8	16h~24h	10擔	44	2001/2/16
29047	06499	SBE	2000	8	18h~02h	10擔	44	2001/2/16
29048	06503	SBE	2000	8	21h~05h	10擔	44	2001/2/16
29049	06502	SBE	2000	8	00h~08h	10擔	44	2001/2/17
29050	06504	SBE	2000	8	04h~12h	10擔	44	2001/2/17
29051	06505	SBE	2000	8	10h~18h	10擔	44	2001/2/17
29052	06506	SBE	2000	8	14h~22h	10擔	44	2001/2/17
29053	06507	SBE	2000	8	21h~05h	10擔	44	2001/2/17
29054	06510	SBE	2000	8	01h~09h	10擔	44	2001/2/18

Table 1 Summary of the ARGOS floats deployed before February 2001 by JAMSTEC/FORSGC.

Fig. 1 Example of ARGOS satellite tracks which possible to communicate with ARGO float.
Lite blue star indicates the ARGO float position.
Black and red crosses on the satellite track show the ARGOS satellite positions when satellite received data from the float without error and with error, respectively.
Red stars show the satellite positions when float position fixed.

2.1 Status of the data communication via ARGOS system in each 5 degrees-grid

Fig. 2 Status of the data communication via ARGOS system in each 5 degrees-grid.

Satellite Name	Band-width (KHz)	Receiver (dBm)	Proc.Units	Link Speed (bits/sec)
NOAA-D	24	-128~-108	4	720
NOAA-H	24	-128~-108	4	960
NOAA-J	24	-128~-108	4	1200
NOAA-K	80	-131~-108	8	2560
NOAA-L	80	-131~-108	8	2560

Table 2 Characteristics of the ARGOS instruments on the NOAA satellites.

2.2 Status of the data communication via ARGOS system in each 6 hours period

Fig. 3 Status of the data communication via ARGOS system in each 6 hours period.

2.3 Status of the data communication every 3 months for the float 29032 and 29033 from April 2000 to June 2001

Fig. 4 Status of the data communication every 3 months for the float 29032 and 29033 from April 2000 to June 2001.

2.4 Correlation between the status of the sea surface and of the data communication

Fig. 5 The receive rate(red triangle)and the error rate(green circle) vs. wave height where floats stayed.

2.5 Correlation between the receive level of the satellites and the status of the data communication

Fig. 6 The receive rate, the error rate(upper panel)and the receive level(middle panel)for each float from Mar. 17, 2001 to Jun. 7, 2001. Periods of the float stayed at the sea surface for each float are also shown in lower panel.

Fig. 7 Communication status in each receive level for the 1st generation satellites(Argos-I;D,H,J).

Fig. 8 Same as Fig.7 except for the 2nd generation satellites(Argos-II;K,L).

3. Consideration

丂	JAMSTEC/FORSGC		University of Washington
丂	The way of calculation by JAMSTEC/FORSGC	The way of calculation by University of Washington	Japan Sea	Atlantic
Receive rate(%)	52	88	86	85
Error rate(%)	21		17	17
Number of data	193		2564	537

Table 3 The receive rate and the error rate for the floats operated by JAMSTEC/FORSGC and University of Washington.

Fig. 9 Orbits of NOAA POES(Polar Orbiting Environmental Satellites) used for the Argos system

丂