Number range CHAPTER**SUMMARY OF PROPOSED CHANGES TO DCPRS CERTIFICATION
STANDARD**

This document contains a set of proposed changes to the DCPRS
Certification Standard, primarily to prepare the DCS for a large step in
capacity by the time GOES R is launched, estimated to be about 2012. The
intent is to double the number of channels that comprise the DCPR by
splitting the existing channels in half. The band from 401.7 MHz to
402.0 MHz will then be able to support 400 channels at 0.75 kHz for 300
bps operation, 200 channels at 1.5 kHz for 1200 bps operation, or a
combination thereof. This channelization will continue into the band
402.0 MHz to 402.1 MHz, GOES International channels, although current
plans are to stay with the current 3.0 kHz channel spacing, i.e., NOAA
will require DCPRS be able to operate at the reduced channel spacing
over the entire 400 kHz. The capacity of the DCS will also be increased
by tightening the timing requirements so more messages can be scheduled
at shorter intervals.

A number of requirements in the Certification Standard need to be
changed to prepare for this improved capacity. NOAA believes the changes
proposed are within the technical capacity shown by the equipment that
has been certified to the existing standard and that the improved
capabilities can be provided at a relatively small increase in cost. In
most cases, the changes must be fully implemented in the operating DCPRS
transmitters and the CDAS and DRGS receive equipment, before actual
changes in system operation can occur. NOAA is therefore providing this
opportunity for review and discussion so the revised certification
standard can be put in place as soon as possible. Vendors and users can
then have as long a period as possible to make the changes to their
equipment.

The proposed changes will tighten the frequency, timing, and filtering
requirements, affecting subsections 2.1, 3.9, 4.2, 4.22, 4.51, and 4.52.
They also reduce the uplink power variation allowed, subsection 4.1.1;
propose the elimination of the interleaver and most prohibited
characters, but double the number of flush bits, subsections 3.1, 3.4,
3.5, and 3.7.1; apply more definitive phase noise requirements,
subsections 4.3.2 and 4.4; and reduce the maximum message length for 300
bps channels, subsections 3.8 and 4.6. Additional clarifications and
minor corrections of typos, etc., have also been included.

Subsections that are not included in the following pages are intended to
be retained as they are.

The proposed changes also include Appendix C, which covers the DCPI
link. This link does not comply with the ITU Power Flux Density (PFD)
requirements as it is presently configured and therefore should be
revised or eliminated as soon as possible. The proposed revision is one
of several possible system designs that could make it of more benefit to
potential users. Users and manufacturers are encouraged to offer
additional or different designs, performance requirements, etc., that
could help keep this link in operation. (If this link is not used,
future spacecraft will be unlikely to provide this service.)

**DESCRIPTION OF THE PROPOSED CHANGES IN NUMERICAL ORDER**

**A. Subsection 2.1**

***[A1.]{.underline} [CURRENT VERSION OF SUBSECTION 2.1:]{.underline}***

2.1 [DCPRS Self- Timed Reporting Mode Requirements]{.underline}

> All DCPRS designated for self-timed operations shall fulfill the
> timing requirements identified below.

2.1.1 [300 BPS Reporting Time Accuracy]{.underline}

> Manufacturer's shall demonstrate that self-timed reporting will have a
> drift of no more than [+]{.underline} 30 seconds per year.
> Manufacturer's may use a combination of analysis with oscillator drift
> data and DCP software utilized.
>
> The DCPRS shall be demonstrated to operate for 48 hours on a
> NOAA/NESDIS assigned channel and time slot. The timing accuracy shall
> not exceed a prorated [+]{.underline} 30 seconds per year.

2.1.2. [1200 BPS Reporting Time Accuracy]{.underline}

> All 1200 BPS DCPRS transmissions shall be within [+]{.underline} 0.5
> seconds of the assigned reporting time with a probability of 99.9%
> within any one year period and at any temperature over a range of
> -40C to +50C. This shall include any inaccuracies associated with
> the initial setting of the clock by the user as specified in paragraph
> 2.1.5 below.

2.1.3 [DCPRS Time Reference]{.underline}

> DCPRS reporting time shall always be with respect to Coordinated
> Universal Time (UTC).

2.1.4. [Inhibiting Transmissions]{.underline}

> Should that the DCPRS clock differs by more than [+]{.underline} 0.5
> seconds from the Coordinated Universal Time (UTC) at time of
> transmission, transmission (including RF carrier) shall be inhibited
> (i.e. shall be canceled). After an inhibited transmission should the
> DCPRS clock be restored to less than [+]{.underline} 0.5 seconds from
> Coordinated Universal Time (UTC), the DCPRS may resume normal
> transmissions.

2.1.5 [Setting and Verifying the DCPRS Clock]{.underline}

> Manufacturer's shall provided a method to enable a user to set the
> DCPRS clock to an accuracy of within [+]{.underline} 0.1 seconds of
> Coordinated Universal Time (UTC). The needed equipment and software
> must be available from the DCPRS vendor to verify the accuracy of the
> DCPRS clock after it has been set.
>
> **NOTE: The requirements in paragraphs 2.1.4 and 2.1.5 are mandatory
> for the 1200 BPS DCP and are optional for the 300 BPS DCP.**

***[A2.]{.underline} [PROPOSED REVISED VERSION OF SUBSECTION
2.1:]{.underline}***

2.1 [DCPRS Self- Timed Reporting Mode Accuracy]{.underline}

> All DCPRS transmissions shall be within [+]{.underline} 0.1 seconds of
> the assigned reporting time with a probability of 99.9% within any one
> year period and over the full range of operating conditions. This
> shall include any inaccuracies associated with the initial setting of
> the clock by the user as specified in paragraph 2.1.3 below.

2.1.1 [DCPRS Time Reference]{.underline}

> DCPRS reporting time shall always be with respect to Coordinated
> Universal Time (UTC). GPS shall be used as the time reference for all
> DCPRS.

2.1.2. [Inhibiting Transmissions]{.underline}

> Should the DCPRS clock differ by more than [+]{.underline} 0.2 seconds
> from the UTC at time of transmission, transmission (including RF
> carrier) shall be inhibited (i.e. shall be canceled). After an
> inhibited transmission, the DCPRS clock shall be restored to less than
> [+]{.underline} 0.1 seconds from UTC before the DCPRS may resume
> normal transmissions.

2.1.3 [Setting and Verifying the DCPRS Clock]{.underline}

> Manufacturer's shall provided a method to enable a user to set the
> DCPRS clock to an accuracy of within [+]{.underline} 0.1 seconds of
> UTC. The needed equipment and software must be available from the
> DCPRS vendor to verify the accuracy of the DCPRS clock after it has
> been set. This shall include a method to predict the clock accuracy at
> specific intervals after the clock has been set as may be necessary
> for normal transmission accuracy.

**B. Subsection 3.1**

***[B1.]{.underline} [CURRENT VERSION OF SUBSECTION 3.1:]{.underline}***

3.1 [DCPRS Data Format]{.underline}. The figure below defines the
required message format.

![](media/image1.wmf)For each of the blocks a "0" = represent 0 degrees
and a "1" represents 180 degrees.

> **^\*^Carrier**: 0.50 seconds for 300 BPS

0.25 seconds for 1200 BPS

> **Clock**: 3 "0 and 180\" degree phase transitions (0-1, 1-0, 0-1)at
> the respective symbol data rate
>
> **Frame Synchronization Sequence (FSS) -** Three possible 15 bit
> Patterns:

+-----------------+-------------------+---------------+---------------+
|                 | No Interleaver    | Short         | Long          |
|                 |                   | Interleaver   | Interleaver   |
+-----------------+-------------------+---------------+---------------+
| Binary          | MSB               | 00            | 00            |
|                 | 000001011001110   | 0100011101001 | 1111100110101 |
+-----------------+-------------------+---------------+---------------+
| Hexadecimal     | 02CE              | 08E9          | 1F35          |
| (implied        |                   |               |               |
|                 |                   |               |               |
| ("0" as MSB)    |                   |               |               |
+-----------------+-------------------+---------------+---------------+

**GOES ID/DCP address:** 31 bits plus LSB assumed as a "0\" to form 4 -
8 bits Bytes

**Flag Word: (LSB)** Bit 1 spare, undefined

> Bit 2 Clock updated since last transmission = 1, not = 0
>
> Bit 3 Data Compression on =1, off = 0 Possible Future Enhancement
>
> Bit 4 Reed Solomon on = 1, off = 0 Possible Future Enhancement
>
> Bit 5 spare, undefined
>
> Bits 6 & 7 ASCII = 10, Pseudo Binary = 11, Binary = 01
>
> (MSB) Bit 8 Odd parity for ASCII formatted data

The FSS consists of three possible 15 bit words where 0 degrees = "0"
and 180 degrees= "1" transmitted at the symbol rate. The left most bit
is transmitted first.

After the FSS is transmitted the remainder of the format is presented as
eight (8) bit bytes. If an interleaver is enabled the respective FSS
word shall be generated. After the FSS is transmitted the GOES ID and
all data shall be scrambled, trellis encoded, and interleaved as defined
in paragraph 3.5 below.

The GOES ID is a 31-bit Bose-Chaudhuri-Hocquenghem (BCH) address with a
zero implied as the 32^nd^ LSB. This address shall be transmitted as the
first 4 bytes of the data in the message in exactly the same manner as
all the other data bytes in the message. For example, given the hex ID
of **CE 12 00 B8**, the first byte transmitted is **CE** hex, followed
by **12** Hex, followed by **00** hex, followed by **B8** hex or
**11001110 00010010 00000000 10111000.**

***B2. [PROPOSED REVISED VERSION OF SUBSECTION 3.1:]{.underline}***

***NOTE: The changes shown below also include the results due to other
changed detailed in following parts of this document.***

3.1 [DCPRS Data Format]{.underline}.

The format for all messages shall meet the following format
requirements.

NOTES: ASCII EOT use for ASCII and Pseudo Binary
Formats![](media/image2.wmf){width="6.480555555555555in"
height="1.2652777777777777in"}

International EOT used for Binary Format

Actual Message Length may not Exceed Fail-Safe Limits

> **Carrier**: 0.50 seconds for 300 BPS
>
> 0.25 seconds for 1200 BPS

**Clock**: 3 symbol periods, first 0 degrees, then 180 degrees, then 0
degrees.

> **Frame Synchronization Sequence (FSS):**
>
> The following 15 bit pattern shall be sent at the appropriate symbol
> rate with \"0\" representing 0 degrees and \"1\" representing 180
> degrees: (MSB) 000001011001110 (LSB) The left most bit is transmitted
> first.

After the FSS is transmitted the GOES ID and all data shall be
scrambled, and trellis encoded, as defined below.

**GOES ID/DCP address:**

31 bits plus an extra \"0\" inserted as the LSB to form 4 - 8 bits Bytes

The GOES ID is a 31-bit Bose-Chaudhuri-Hocquenghem (BCH) encoded address
with a zero included as the 32^nd^ LSB. This address shall be
transmitted as the first 4 bytes of the data in the message in exactly
the same manner as all the other data bytes in the message. For example,
given the hex ID of **CE 12 00 B8**, the first byte transmitted is
**CE** hex, followed by **12** Hex, followed by **00** hex, followed by
**B8** hex or **11001110 00010010 00000000 10111000.**

**Flag Word: (LSB)** Bit 1 spare, undefined

> Bit 2 Clock updated since last transmission = 1, not = 0
>
> Bit 3 Data Compression on =1, off = 0 Possible Future Enhancement
>
> Bit 4 New Coding on = 1, off = 0 Possible Future Enhancement (Code
> format not yet defined)
>
> Bit 5 spare, undefined
>
> Bit 6 = 1 if ASCII or Pseudo Binary, otherwise = 0

Bit 7 = 1 if Pseudo Binary or Binary, otherwise = 0

> (MSB) Bit 8 Odd parity for ASCII formatted data

**C. Subsection 3.2**

***[C1.]{.underline} [CURRENT VERSION OF SUBSECTION 3.2:]{.underline}***

3.2 [Data Scrambling]{.underline}

At the beginning of the GOES ID all DCP data must be scrambled. Each
data byte is scrambled by "exclusive ORing" (XOR) the byte with a byte
from the following 40 byte table. The first byte is XORed with the first
byte in the table (53 hex). The next byte is XORed with the second byte
in the table (12 hex), and so on. After the 40th byte has been scrambled
the next scramble byte to be used is the first byte (53 hex). The below
table is to be used in a circular fashion throughout the message.

  ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----
  53   12   72   B2   54   62   AA   E4   DB   A7   56   08   A8   09   B4   BF   61   DC   50   E3

  AB   7F   00   87   6D   F5   58   CC   CF   3E   E7   2A   7E   9B   5C   4D   CE   A5   3C   0A
  ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----

This array is treated as a single binary string where each data binary
pair generates one symbol. BAD hex is the first scrambled symbol output
and recycles after 160 input symbols. This array shall be cycled through
as many times as required for the duration of the message data.

***[C2.]{.underline} [PROPOSED REVISED VERSION OF SUBSECTION
3.2:]{.underline}***

3.2 [Data Scrambling]{.underline}

Starting with the first bit of the GOES ID, all DCPRS data shall be
scrambled. The DCPRS serial data stream shall be "exclusive ORed" (XOR)
with the serial binary string represented by the table below. It is
shown as 40 bytes using hex symbols for convenience, and shall be used
in a circular fashion throughout the message.

  ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----
  53   12   72   B2   54   62   AA   E4   DB   A7   56   08   A8   09   B4   BF   61   DC   50   E3

  AB   7F   00   87   6D   F5   58   CC   CF   3E   E7   2A   7E   9B   5C   4D   CE   A5   3C   0A
  ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----

For example, the first byte of the GOES ID example, CE (hex), would be
XOR with the first byte in the table, 53 (hex), i.e., the serial string
1100 1110 XOR with the serial string 0101 0011 to produce 1001 1101, or
9D (hex). Then the second byte of the GOES ID, 12 (hex), would be XOR
with the second byte in the table, 12 (hex), to produce 00 (hex), and so
on. After the last byte of the table 0A (hex), has been XOR with the
40th byte of the DCPRS message, the table would be cycled and the 41st
message byte XOR with the first byte in the table, 53 (hex). This
sequence would continue as many times as required for the duration of
the message, including the EOT and flush bits.

D.  **Subsection 3.4**

***[D1.]{.underline} [CURRENT VERSION OF SUBSECTION 3.4:]{.underline}***

3.4 [Encoder Flush]{.underline}

At the end of the message after transmitting the EOT an additional 16
zero (0) data bits shall be provided to flush the encoder. After the
16^th^ flush bit is transmitted, the interleaver, if used, shall be
unloaded per para. 3.5.2, the phase should be brought to zero and the
carrier power shall be turned off.

***[D2.]{.underline} [PROPOSED REVISION TO SUBSECTION
3.4:]{.underline}***

3.4 [Encoder Flush]{.underline}

At the end of the message after transmitting the EOT, an additional 32
zero (0) data bits shall be provided to flush the encoder and decoder.
After the 32^nd^ flush bit is transmitted, the phase should be brought
to zero and the carrier power shall be turned off.

**E. Subsection 3.5**

This subsection describes interleaver requirements, however, NOAA\'s
technical advisors can find no benefit provided by these interleavers in
this application, but have found there is a significant \"cost\" due to
the additional transmission time needed to unload the interleaver.

**[IT IS THEREFORE PROPOSED TO DELETE SUBSECTION 3.5 IN ITS
ENTIRETY.]{.underline}**

*If any user or manufacturer has any data indicating any benefit from
using an interleaver in the DCS, they should provide it so NOAA can
perform a cost/benefit analysis.*

**F. Subsection 3.7.1**

***[F1.]{.underline} [CURRENT VERSION OF SUBSECTION
3.7.1:]{.underline}***

3.7.1 [Prohibited Characters]{.underline}

For ASCII or Pseudo Binary format the following control characters are
prohibited: DLE, NAK, SYN, ETB, CAN, GS, RS, SOH, STX, ETX, ENQ, ACK,
and EOT. For DCPRS certification testing a set of five messages of at
least 500 characters in length shall be sent in a pre-defined ASCII
character set. The test demodulator output will be capable of extracting
this transmitted text.

For binary mode certification a fixed set of binary values is sent five
times. The string should be at least 256 bytes long. The precise format
and error checking for HDR binary transmissions is TBD.

***[F2.]{.underline} [PROPOSED REVISION TO SUBSECTION
3.7.1:]{.underline}***

a\. NOAA proposes to lift the prohibition on all characters except EOT.
If any interested party has any reason to suggest the prohibition should
be retained for any other character, they are requested to notify NOAA
as soon as possible.

b\. NOAA requests any interested party to offer a specific format and
performance checking method for HDR binary transmissions so that a
formal standard can be set.

**G. Subsection 3.7.2**

***[G1.]{.underline} [CURRENT VERSION OF SUBSECTION
3.7.2:]{.underline}***

3.7.2 [End Of Transmission (EOT)]{.underline}

ASCII and Pseudo Binary Format Mode - An EOT code word, bit pattern
00000100 - LSB first, shall be sent immediately after the last symbol of
sensor data. This bit pattern is an ASCII EOT with odd parity.

Binary Mode - An (EOT) code word, bit pattern
1100011110010101110100000100 - LSB first, shall be sent immediately
after the last symbol of sensor data. This bit pattern is identical to
that required for international DCPRS certification.

***[G2.]{.underline} [PROPOSED REVISED VERSION OF SUBSECTION
3.7.2:]{.underline}***

3.7.2 [End Of Transmission (EOT)]{.underline}

ASCII and Pseudo Binary Format Mode - An EOT code word, bit pattern
00000100, transmitted with the LSB first, shall be sent immediately
after the last symbol of sensor data. This bit pattern is an ASCII EOT
with odd parity.

Binary Mode - An (EOT) code word, 0110 0011 1100 1010 1101 1101 0000
0100 with the LSB transmitted first, shall be sent immediately after the
last symbol of sensor data. This bit pattern is identical to that
required for international DCPRS certification except an additional zero
(0) is inserted as the MSB to provide an even number of bits to be sent
to the encoder.

**H. Subsection 3.8**

This subsection defines the maximum message length, but it is, partly,
in conflict with the fail-safe message length requirement in subsection
4.6.

**[IT IS THEREFORE PROPOSED TO DELETE SUBSECTION 3.8 IN ITS
ENTIRETY.]{.underline}**

**I. Subsection 3.9**

This subsection requires that the room temperature frequency adjustment
be within 25 Hz. NOAA intends to require that the transmitted carrier
frequency be held to much better accuracy than was previously required,
see item L below. However, NOAA has also concluded that the critical
parameter is the worst case frequency variation from perfect accuracy,
not precision of adjustment.

**[IT IS THEREFORE PROPOSED TO DELETE SUBSECTION 3.9 IN ITS
ENTIRETY.]{.underline}**

**J. Subsection 4.1.1**

***[J1.]{.underline} [CURRENT VERSION OF SUBSECTION
4.1.1:]{.underline}***

4.1.1 [RF Power Output]{.underline}

> For 300 bps the DCPRS shall have a nominal EIRP of 48 dBm - Carrier
> only and a maximum EIRP of 50 dBm under any combination of power
> supply or temperature variation.
>
> For 1200 bps the DCPRS shall have a nominal EIRP of 51 dBm - Carrier
> only and a maximum EIRP of 53 dBm under any combination of power
> supply or temperature variation.
>
> Note: During the random modulation portion of the message the output
> power will be 1 dB less (See Appendix E paragraph 1- test notes for a
> discussion of RMS transmitted power).
>
> DCPRS EIRP testing shall include a test to show the transmit amplifier
> 1 dB compression point. The DCPRS phase noise measurement shall be
> made with the transmitter operated at or above the 1 dB compression
> point.

***[J2.]{.underline} [PROPOSED REVISION TO SUBSECTION
4.1.1:]{.underline}***

4.1.1 [RF Power Output]{.underline}

For 300 bps, the DCPRS shall have a maximum EIRP of 50 dBmi and a minium
EIRP of 47 dBmi. For 1200 bps, the DCPRS shall have a maximum EIRP of 53
dBmi and a minium EIRP of 50 dBmi. These limits shall be met under any
combination of operational conditions.

NOTE: The satellite transponder has been designed to operate over the
uplink EIRPs listed above. Levels higher that the maximum will tend to
overload the transponder and are prohibited. Levels less than the
minimum may not provide an acceptable error rate when a large number if
channels are simultaneously active. The minimum is cited because it is
the lower limit of the system design, but users are permitted to use
lower EIRP at their own risk.

**K. Subsection 4.2**

***[K1.]{.underline} [CURRENT VERSION OF SUBSECTION 4.2:]{.underline}***

4.2 [GOES DCS Operating Frequency Requirements]{.underline}

The GOES domestic DCS operates at UHF from 401.7 MHz to 402.0 MHz with
either 200- 1.5 kHz channels @ 100/300 bps, 100 - 3.0 kHz channels @
1200 bps or a combination thereof. The GOES international DCS operates
from 402.0 MHz to 402.1 MHz with 33-3kHz channels. Although the 300 bps
and 1200 bps DCPRS has not been adopted or approved for use in the
international DCS, 3 kHz tuning from 402.0 MHz to 402.1 MHz is required
for all HDR DCPRS.

***[K2.]{.underline} [PROPOSED REVISION TO SUBSECTION
4.2:]{.underline}***

4.2 [GOES DCS Operating Frequency Requirements]{.underline}

The DCPRS shall be able to operate at any of the channel center
frequencies designated below.

For DCPRS operating at 300 bps:

The DCPRS shall be able to tune to 532 channels at 750 Hz increments,
from 401.701000 MHz to 402.099250 MHz. The channel 1 center frequency
shall be 401.701000 MHz, channel 2 center frequency shall be 401.701750
MHz, channel 3 center frequency shall be 401.702500 MHz, etc., up to
channel 532 at 402.099250 MHz

For DCPRS operating at 1200 bps:

The DCPRS shall be able to tune to 266 channels at 1500 Hz increments,
from 401.701000 MHz to 402.098500 MHz. The channel 1 center frequency
shall be 401.701000 MHz, channel 2 center frequency shall be 401.702500
MHz, channel 3 center frequency shall be 401.704000 MHz, etc., up to
channel 266 at 402.098500 MHz

**L. Subsection 4.2.2**

***[L1.]{.underline} [CURRENT VERSION OF SUBSECTION
4.2.2:]{.underline}***

4.2.2 [Frequency Stability, Long Term]{.underline}

The DCPRS output frequency shall maintain a long term aging stability of
[+]{.underline} 0.5 PPM and be permitted an additional [+]{.underline}
0.5 PPM of drift under any combination of power supply variation or
temperatures set forth in paragraph 4.0 on any channel frequency defined
in Appendix D. The output frequency shall be maintained to within
[+]{.underline} 425 Hz of the channel center.

***[L2.]{.underline} [PROPOSED REVISION TO SUBSECTION
4.2.2:]{.underline}***

4.2.2 [Frequency Stability, Long Term]{.underline}

The DCPRS output frequency shall be maintained to within [+]{.underline}
30 Hz of the channel center frequency due to any combination of
operational conditions and on any channel frequency.

**M. Subsection 4.3.2**

***[M1.]{.underline} [CURRENT VERSION OF SUBSECTION
4.3.2:]{.underline}***

4.3.2 [DCPRS 8-ary Modulator Stability]{.underline}

The 8-ary modulator shall maintain a stability/accuracy of
[\<]{.underline} [+]{.underline} 2.5 degrees under any combination of
power supply or temperature variation as defined in paragraph 4.0 (See
Appendix E - GOES DCS Certification Test Notes Paragraph 3.0 Phase
Measurement).

***[M2]{.underline} [PROPOSED REVISION TO SUBSECTION
4.3.2:]{.underline}***

**[IT IS THEREFORE PROPOSED TO DELETE SUBSECTION 4.3.2 IN ITS
ENTIRETY.]{.underline}**

(NOAA intends to require improved phase accuracy, but will combine all
phase stability and accuracy parameters into one requirement. See item N
below.)

**N. Subsection 4.4**

***[N1.]{.underline} [CURRENT VERSION OF SUBSECTION 4.4, INCLUDING 4.4.1
AND 4.4.2:]{.underline}***

4.4 [DCPRS Phase Noise]{.underline}

4.4.1 [DCPRS Carrier Phase Noise]{.underline}

The DCPRS carrier phase noise shall be \< 2.5 degrees RMS under any
combination of power supply or temperature variation as defined in
paragraph 4.0.

DCPRS RMS phase noise is to be measured during transmission of carrier
only. First the test set up residual noise from the receiver and signal
generator shall be measured. This should be \< 0.2 degrees. Then measure
the DCPRS phase noise. Subtract the residual set up phase noise from the
DCPRS phase noise.

The DCPRS phase noise measurement is to be made at the "Q" output of the
test demodulator. While making this measurement the test signal should
be observed on an oscilloscope. Test data can be extracted from the test
demodulator program or by using RMS voltmeter with a 2000 Hz response at
the 1200 BPS data rate.

4.4.2 [DCPRS Dynamic Phase Noise (Inter Symbol Interference
(ISI))]{.underline}

The DCPRS dynamic phase noise or ISI shall be [\<]{.underline} 1.5
degrees RMS (see Appendix E - GOES DCS Certification Test Notes Para.
2.0 Phase Error Budget) which provides a recommended measurement
process.

***[N2.]{.underline} [PROPOSED REVISION TO SUBSECTION
4.4:]{.underline}***

4.4 [DCPRS Phase Noise]{.underline}

The total phase noise and bias due to all causes and under any
combination of operational conditions, shall be less than 3.0 degrees
RMS. (See Appendix E for approved measurement procedures.)

**O. Subsection 4.5.1**

***[O1.]{.underline} [CURRENT VERSION OF SUBSECTION
4.5.1:]{.underline}***

4.5.1 [Narrow Band Transmit Spectrum]{.underline}

The first modulation sideband is defined as the energy around the
carrier frequency extending to the theoretical first spectral nulls on
both the positive and negative sides of the carrier. For NRZ-PSK
modulation this is from F~C~ - R~S~ to F~C~ + R~S~, where F~C~ is the
carrier frequency and R~S~ is the symbol rate. The second sideband is
defined as the frequency band from F~C~ + R~S~ to F~C~ + 2R~S~ and from
F~C~ - R~S~ to F~C~ - 2R~S~. Third and higher sidebands are defined in a
similar manner using 3R~S~, 4R~S~, etc.

The first sideband is the desired signal, all other sidebands are
undesired.

When modulated with a random data stream, the 300 and 1200 bps signals
shall produce sidebands with peak energy equal to, or less than, the
following values.

Second sideband -15 dBc

Third sideband -25 dBc

Fourth sideband -35 dBc

Fifth and higher sidebands -45 dBc

Note: The sideband levels measured shall be referenced to the level of
the unmodulated carrier.

**Recommended Test Process:**

The transmitter under test shall be operated into a 50 ohm load and at
its maximum rated output power level. All measurements of the carrier
and sideband levels shall be made with the spectrum analyzer controls
set as follows:

Residual Bandwidth 30 Hz

Video Bandwidth 10 Hz

Sweep time 50 seconds

Level Sensitivity 5 dB per division

The frequency span shall be 5000 Hz for 1200 bps and 1250 Hz for 300 bps
measurements.

These measurements will require the use of test data sequences that are
longer than normally permitted to provide sufficient sweep time for
accurate measurement.

NOTE: See Appendix E Test Notes for Random Data plots of the above
transmit spectrum with the HDR Improved Test Transmitter.

***[O2.]{.underline} [PROPOSED REVISION TO SUBSECTION
4.5.1:]{.underline}***

4.5.1 [Narrow Band Transmit Spectrum]{.underline}

The transmit spectrum shall be shaped using a Square-Root Raised Cosine
(SRRC) filter with an excess bandwidth factor () of 1.0. The filter
implementation shall match the theoretical SRRC shape to within 1 dB
between the -20 dB points on the theoretical curve.

When modulated by a data stream using the scrambler defined in
subsection 3.2 above, the total power produced by the DCPRS outside of
the filter roll-off bandwidth, due to signal sidebands, noise, and any
other undesired emissions, when measured in any 100 Hz band, shall be at
least 36 dB below the total power that is transmitted in the necessary
bandwidth for 300 bps channels and 40 dB for 1200 bps channels. (The
necessary bandwidth shall be from (carrier frequency - symbol rate in
Hz) to (carrier frequency + symbol rate in Hz)).

**P. Subsection 4.5.2**

***[P1.]{.underline} [CURRENT VERSION OF SUBSECTION
4.5.2:]{.underline}***

4.5.2 [Mid-Band Transmit Spectrum]{.underline}

With the transmitter set with a random 8 PSK modulation the Mid-Band and
Harmonics shall be as set forth below:

For the 300 bps data rate at F~o~ [\>+]{.underline} 1500 Hz
[\<]{.underline}-60 dBc

For the 1200 bps data rate at F~o~ \>[+]{.underline} 10000 Hz
[\<]{.underline}-60 dBc

***[P2.]{.underline} [PROPOSED REVISION TO SUBSECTION
4.5.2:]{.underline}***

4.5.2 [Mid-Band Transmit Spectrum]{.underline}

At any frequency separated by more than 250% of the necessary bandwidth
from the carrier frequency, the total power emitted in any 4 kHz band
shall be as set fourth in Recommendation ITU-R SM.329, Table 2 Spurious
Limits -- Category A:

43 + 10 Log(P) or 60 dBc, whichever is less stringent

Where P is the mean power applied to the antenna transmission line

> This requirement shall be met for any type of transmission and under
> any combination of operational conditions.

**Q. Subsection 4.6**

***[Q1.]{.underline} [CURRENT VERSION OF SUBSECTION 4.6:]{.underline}***

4.6 [Fail-safe Operating Requirements]{.underline}

An independent or separate fail-safe circuit shall be provided to
prevent a DCPRS from operating in an uncontrolled fashion. This
independent circuit must "permanently " shut off the transmitter if any
of two conditions are violated. These two conditions are:

1.  Message is too long. For 300 BPS a DCP message length of
    [\>]{.underline} 270 seconds shall trip the fail-safe. For 1200 BPS
    a DCP message length of [\>]{.underline} 105 seconds shall trip the
    fail safe.

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1.  Message sent is too soon. There shall be a minimum of 30 seconds
    off-time between successive transmissions. If a second message is
    transmitted before 30 seconds has expired, then the fail-safe shall
    be tripped.

The fail-safe capability must be demonstrated for all conditions over
the defined operating a -40^°^ C to 50C temperature range and over the
required power supply voltage variation. Removal of DC power from the
DCPRS shall not affect the operation of this function.

**Note: The above term "permanently" requires a manual intervention or
reset of the DCPRS in order to restore the unit for operational use in
the DCS.**

***[Q2.]{.underline} [PROPOSED REVISION TO SUBSECTION
4.6:]{.underline}***

4.6 [Fail-safe Operating Requirements]{.underline}

An independent or separate fail-safe circuit shall be provided to
prevent a DCPRS from operating in an uncontrolled fashion. This
independent circuit must "permanently " shut off the transmitter if
either of the following two conditions are violated.

2.  Message is too long. A DCPRS message length \>105 seconds shall trip
    the fail safe for either 300 bps or 1200 bps transmissions.

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2.  Message is sent too soon. There shall be a minimum of 30 seconds
    off-time between successive transmissions. If a second message is
    transmitted before 30 seconds has expired, then the fail-safe shall
    be tripped.

The fail-safe capability must be demonstrated over the full range of
operating conditions. Removal of DC power from the DCPRS shall not
affect the operation of this function.

**Notes:**

**1. The above term "permanently" requires a manual intervention or
reset of the DCPRS in order to restore the unit for operational use in
the DCS.**

**2. The Inhibiting Transmission requirement of subsection 2.1.2 is
specifically NOT included in this subsection.**

**R. Appendix C**

NOTE: The current DCPI link does not meet the ITU PFD requirement of
-152 dBW/m2 in a 4 kHz bandwidth. The satellite EIRP must not exceed
40.1 dBmi to meet this PFD limit, which is 5 -- 6 dB below the current
DCPI transmit EIRP for the current system.

**[SOME CHANGE WILL BE NECESSARY]{.underline}**

The proposed revision, included in section R2 below, is provided as an
(incomplete) example of one possible set of changes that is thought
might be the basis for an acceptable DCPI system. Any interested party
is encouraged to propose additional or alternative content for this
item.

***[R1.]{.underline} [CURRENT VERSION OF APPENDIX C:]{.underline}***

**Appendix C - Interrogate DCP Receive Requirements**

3.1 [Received Frequency Characteristics]{.underline} - The DCP received
radio-frequency (RF) shall be as follows:

> a\. The Geostationary Operational Environmental Satellite (GOES) East
> frequency - 468.8375 MHz.
>
> b\. The GOES West frequency - 468.8125 MHz or 468.825 MHz.
>
> c\. Furthermore, these frequencies shall be selectable without
> requiring realignment.

3.2. [Interrogate Receive Signal Characteristics]{.underline}

> a\. [Data Format]{.underline} - The DCP shall be capable of receiving
> and demodulating the following sequence:
>
> 1\) 4 bit Binary Coded Decimal (BCD) time code followed by,
>
> 2\) 15 bit MLS sync word (bit pattern 100010011010111) followed by,
>
> 3\) 31 bit BCH interrogate address word (e.g. bit pattern
> 0011010010000101011101100011111 -- MSB first in Hexadecimal. The DCPRS
> shall respond to one or more assigned addresses within 1 second. The
> DCPRS shall respond whenever the received sequence is exact or within
> two bits of the assigned address(es).
>
> b\. [Acquisition Time]{.underline}
>
> The receiver shall acquire lock-on to the interrogation signal format
> in two minutes or less, from standby conditions when the interrogation
> signal carrier is within [+]{.underline} 100Hz. The acquisition shall
> be accomplished in the presence of modulation.
>
> c\. [Level]{.underline}
>
> The DCP shall lock-on and demodulate the interrogation signal over the
> range of -100 dBm maximum to -130 dBm minimum centered at the carrier
> frequencies identified in paragraph 3.1 above measured at the receiver
> antenna terminals.
>
> d\. [Mean Time to Cycle Slip (MTCS)]{.underline}
>
> The MTCS for the carrier tracking loop shall be equal to or greater
> than 1 minute.

***[R2.]{.underline} [PROPOSED REVISION TO APPENDIX C:]{.underline}***

**Appendix C - Interrogate DCP Receive Requirements**

C.1 [Received Frequency Characteristics]{.underline} - The DCP received
radio-frequency (RF) shall be as follows:

a.  The GOES East frequency - 468.8375 MHz

b.  The GOES West frequency - 468.8125 MHz

c.  Test/spare frequency - 468.8250 MHz

C.2. [Interrogate Signal Characteristics]{.underline}

a.  Modulation -- BPSK NRZ-L

b.  Data Rate (user) -- 1200 bps

c.  FEC Code -- Rate 1/2 convolutional inner code plus Reed-Solomon
    (255, 223) outer code. (Same as will be used for LRIT and EMWIN on
    GOES N/O/P.)

d.  RF Data Rate -- 2736 bps

e.  Data Filtering -- SRRC (for transmitters and receivers) with excess
    bandwidth factor () of 1.0 (Same as will be used for LRIT and EMWIN
    on GOES N/O/P.)

f.  Sideband Attenuation -- -30 dBc minimum

g.  Necessary Bandwidth -- 5472 Hz

h.  Satellite EIRP -- 40.0 dBmi

i.  Required bit error rate -- 10^-6^

j.  Worst Case DCPRS G/T -- -22 dB/K

k.  Worst Case DCPRS Demod/Decode Implementation Loss -- 2.0 dB

l.  Receiver tracking loop bandwidth -- 100 Hz (minimum)

**[Other Parameters:]{.underline}**

Any interested parties are requested to offer other parameters to be
included in the specification, or alternatives to those suggested above.
At the very least, a definition of the digital interface, the content to
be permitted, and the digital format, will need to be added to the above
partial description, or any alternative that may be proposed.

NOTE:

The following link budget is attached for reference, showing the
expected performance of a GOES N and a receive system that meets the
above requirements. (It is not intended to be part of Appendix C, but is
provided for reference only.)

Anyone who wishes to offer a different implementation for a new DCPI
system must be compatible with the spacecraft capabilities shown
therein. The performance of the GOES N/O/P satellites is essentially
"cast in concrete."

![](media/image3.wmf)

**S. Appendix D**

The current Appendix D is a listing of all 266 channels that are
possible with the current frequency plan, with separate listings for 300
bps and 1200 bps channel designations. The proposed frequency plan would
require a list of double that length for the 532 channels that are
basically defined in subsection 4.2.

Is this listing necessary as part of this document?

Comments are requested.

**T. Appendix E**

The existing content of this appendix will no longer be applicable if
the changes proposed above are implemented. Suggestions are requested.

One subsection that could be included is the phase noise budget for the
end-to-end link.

**Link Phase Noise Budget**

A phase noise budget is proposed for the entire DCS so that each part of
the system can be individually tested, independent of the other parts,
and still be assured that all components that meet their assigned
requirement will provide acceptable system function.

The proposed budget for the DCPRS is derived as follows :

1.  The demodulators are expected to normally operate with a bit error
    rate near 1 in 10^7^, and it is desired that errors due to phase
    noise should be about two orders of magnitude better, i.e., about 1
    in 10^9^.

2.  Phase noise is a normal or Gaussian distributed variable, with
    standard deviation, . Therefore the dual-tail, Normal Error
    Integral gives a probability of 1 in 10^9^ that it exceeds 6.1 from
    its mean value.

3.  The total phase error required to cause bit errors in an 8PSK
    demodulator is 22.5 degrees, half of the 45 degree phase shift
    between each of the nominal phase states.

4.  This document proposes a DCPRS phase offset/bias 1.0 degrees.

5.  22.5 - 1.0 = 21.5 and 21.5 / 6.1 = 3.52

6.  Therefore, the total system phase noise must be 3.5 degrees or less.

7.  The phase noise in the GOES N primary and redundant DCPR
    transponders has been measured at 0.5 degrees, worst case. Therefore
    an allocation of 1.0 degrees is proposed for all of the GOES N and
    GOES R series of satellites.

8.  The DCPRS phase noise required by the current Certification
    Standards is 2.5 degrees.

9.  The phase noise allocation proposed for the dual down conversion
    receive path at WCDAS is 2.0 degrees.

10. The phase noise allocation proposed for the additional down
    conversion at the input to the demodulators at WCDAS is 1.0 degrees.

11. The RSS for all these components of the system phase noise is 3.5
    degrees.

The integration limits for calculating phase noise are 10 Hz and 150 Hz
for the 300 bps channels and 36 Hz and 600 Hz for the 1200 bps channels.
These are the values that will apply to the demodulators at WCDAS and
have been set as the standard to be used for the satellite and DCPRS
requirements. It is recommended that these values also be used in the
design of future demodulators for WCDAS and/or DRGS, at these data
rates.