Campbell ST-21 Information

COMPONENTS

ST-21

Argos Satellite Transmitter

Overview

Campbell Scientic’s ST-21* is a Service Argos-certied Platform
Transmitter Terminal (PTT ) that transfers data from the datalog­ger site to the Argos Data Collection and Location System via
NOAA polar orbiting satellites. This transmitter is well suited for

Benets and Features

Well-suited for remote meteorological and environmental
data-collection applications, including mobile and high­latitude installations

Compatible with Campbell Scientic’s CR800, CR850, CR1000,
and CR3000 dataloggers

Provides uplink capability for up to eight unique ID codes,
frequencies, and repetition periods

Supports up to seven independent Argos data buers that can
be populated in real-time

remote meteorological and environmental data collection ap­plications, including mobile and high-latitude installations. The
ST-21 is compatible with our newer dataloggers.

Transmits variable-length Argos messages with either 20- or
28-bit ID codes

Allows researchers to forgo a rigorous certication process
Includes an autorepeat feature that allows the ST-21 to repeat

data without host intervention
Provides a fail safe feature that alerts users upon communica-

tion link or host failure
Allows the ID and repetition rates to be set in real-time or by

Campbell Scientic

*While Campbell Scientic’s ST-21 Argos PTT is based on Telonics’ ST-21, they are not equivalent; our ST-21 includes a case, voltage regulator, and our
SDC communication interface.

questions & quotes: 435.227.9000

www.campbellsci.com/st-21

Argos System, Pass Frequency, and Pass Duration

Service Argos data transceivers are aboard two of NOAA’s sun­synchronous, polar-orbiting satellites. The polar orbits allow a
single satellite to provide coverage of the entire Earth’s surface as
it rotates through the plane of the orbit.

The satellite can receive and decode data from several PTTs
simultaneously, removing the timing constraints associated with
GOES transmissions. In applications where the PTT is mobile (e.g.,
drifting oceanographic buoys), Argos can use Doppler shift data
gleaned from several received transmissions to locate a PTT to
within 150 m. The satellites’ relatively low orbit of 850 km permits
the PTT to operate with a small antenna and power supply.

The Service Argos transceiver receives messages from the PTT
when passing overhead. Pass duration is 10 minutes on average.
The orbital period for each satellite is 1 hour, 42 minutes; passes
per day vary from six at the Equator to 28 at the poles. Typical
transmissions occur in under 1 second and are spaced at 200
second intervals (±6 seconds).

The ST-21 transmitter supports up to eight Argos ID codes, allow­ing transmission of seven unique data sets per expected satel­lite pass. Because the PTT does not “know” when the satellite is
overhead, messages are repeated to ensure reception. Each data
transmission includes up to 32 bytes.

Our CR800, CR850, CR1000 and CR3000 dataloggers can format
the data as bits per data point, allowing the user to select the
resolution used for each data point.

Assuming a repetition period of 200 seconds, and two 32 byte
buers are used with one 20 bit ID number, the average data
throughput by latitude is provided below.

Message repeat intervals, Argos ID numbers, and duty cycles are
changed at Campbell Scientic or by using the datalogger. Data
must be decoded by the user, or by Service Argos. The datalog­ger’s CS I/O port provides power and I/O connections to the
transmitter using the standard SC12 cable.

Average Data Throughput Table

Site Latitude

0° 80 minute 6 7 8 448

15° 88 minute 8 8 9 512

30° 100 minute 8 8 12 576

45° 128 minute 10 11 12 704

55° 170 minute 16 16 18 1024

65° 246 minute 21 22 23 1408

75° 322 minute 28 28 28 1792

Cumulative Visibil-

ity Over 24 hrs

Minimum Number

of Passes Per 24 hrs

Mean Number of
Passes Per 24 hrs

Maximum Number

of Passes Per 24 hrs

Average Bytes Per

24 hrs

90° 384 minute 28 28 28 1792

Platform Transmitting Terminal
(PTT) Equipment

ST-21 Argos transmitter (includes an SC12 cable)
CR800, CR850, CR1000, or CR3000 datalogger
12022 antenna (includes antenna cable and mounting bracket)
Environmental enclosure (ENC12/14, ENC14/16, ENC16/18,

ENC24/30, or ENC24/30S)
Power supply consisting of our BP12 12-Ahr or BP24 24-Ahr

battery pack, CH100 or CH200 regulator, and SP10 10-W or
SP20 20-W solar panel

Retrieving Data from the
Ground Receiving Station

Choose one of the following methods:

Phone modem with MNP level 4 error cor­rection (most Hayes-compatible modems
contain this error-checking protocol; check
the operator’s manual for your modem)
and user-supplied communication software
(e.g., Procomm Plus, Crosstalk).

Internet
Telnet
Email

The 12022 Argos Marine
Half Wave Antenna is a
401 MHz antenna that
includes a 17 ft cable.

◀

Subscribing to Argos

To use the Argos system, you must receive formal permission
from Service Argos and pay a fee. The data must be used for envi­ronmental purposes. Examples include meteorological/hydrolog­ical stations, ship tracking, volcano monitoring, and seismic data.
To subscribe to Argos, the following steps must be completed:

1. Obtain a Program Application Form from the Service Argos
website (www.argosinc.com) or from one of the following:

North America

CLS America, Inc.
1441 McCormick Drive, Suite 1050
Largo, MD 20774
Tel [phone]
E-mail: usero[e-mail]
Website: www.clsamerica.com

Europe

CLS/Service Argos
8-10, rue Hermes
Parc Technologique du Canal
31520 Ramonville Saint-Agne, France
Tel [phone]
Email: [e-mail]
Website: www.cls.fr

2. Fill out and submit the application form to the appropriate
Service Argos oce. Service Argos will send you a program
review stating whether your program has been approved.

3. Following approval, send a Technical File that describes
the required data processing and type of results to the
appropriate Service Argos oce.

4. Complete and return a Service Agreement to the appro­ priate Service Argos oce.

Typical System

Service Argos

NOAA Satellite

The environmental
enclosure houses the
transmitter, datalogger,
and power supply

Platform Transmitting Terminal (PTT)

Campbell Scientic, Inc.

815 W 1800 N

Logan, UT 84321-1784

[phone]

www.campbellsci.com

Ordering Information

Argos Transmitter

When ordering the transmitter, the customer needs to provide Campbell
Scientic with the number of buers, repetition rate, decimal ID, Dex ID,
frequency, and fail safe information.

ST-21 Argos Platform Transmitter Terminal PT T

Specications

Operating Temperature Range: -30° to 70°C
CE Compliant
Supply Voltage: 12 V, nominal
Output Impedance: 50 Ω
High Power Level: 800 mW typical; 27 to 31 dbm
Argos Transmission Frequency: 401.618 to 401.680 MHz
Modulation (BPSK): -1.1 to +1.1 ±0.1 radians
Spurious Emissions: -45 dB

Antenna Cable/Bulkhead Installations

12022 ARGOS 0 dBd OMNI Marine 1/2 Wave Dipole Antenna

3659 1 in. IPS Unthreaded Aluminum Pipe, 12 inches long for mount-

ing the antenna to a crossarm via the CM210.

CM210 Crossarm-To-Pole Mounting Kit for attaching the aluminum pipe

to a crossarm.

21212 Black Cold Shrink Tape, 10ft long Roll, 1in wide used to help

protect the antenna connections.

Length: 19.05 cm (7.5 in)
Height: 5.72 cm (2.25 in)
Width: 3.18 cm (1.25 in)
Weight: 224 g (7.9 oz)

Current Drain at 12 Vdc

Quiescent: 1.12 mA
Transmitting: 375 mA

USA | AUSTRALIA | BRAZIL | CANADA | CHINA | COSTA RICA | ENGLAND | FRANCE | GERMANY | SOUTH AFRICA | SPAIN

|

|

|

|

© 2010, 2013

Campbell Scientic, Inc.

August 29, 2013