[IGSMAIL-8559] Announcing JTRF2020-u2022

[Claudio Abbondanza]

Dear JTRF Users,

We are pleased to announce that JTRF2020-u2022, the JPL-Caltech first update 
of JTRF2020, is ready to be released and distributed to the community.
JTRF2020-u2022 has been computed by running SREF -the square-root information 
filter and smoother algorithm developed at JPL to estimate terrestrial
reference frames- in update mode. 

In computing JTRF2020-u2022, SREF adopts the conceptual framework of Bayesian
update inherent to any Kalman filter formulation: the latest estimate
of JTRF2020 state and its covariance (YEAR 2020, DOY 366, GPS Week 2138) gets
uploaded and subsequently updated by assimilating at daily intervals the extended
frame inputs made available by IGS (IGSR3-igr3.atx), IVS (ivs2023b), ILRS (ilrsav86),
and IDS (idswd23) from 2021 through the end of 2022 (DOY 330, GPS Week 2237).
Afterwards, with SREF running in forecast mode, station positions are
predicted through the end of 2027 (DOY 365, GPS Week 2503).

JTRF2020-u2022 consists of 2556 daily "gzipped" SINEX files in 'VARIANCE-COVARIANCE'
format containing geocentric coordinates along with their full covariance 
from 931 stations, the full JTRF2020 network. It is worth observing that, although 
new space-geodetic stations acquiring observations after the end of 2020 have been 
made available and included in the frame inputs by the Technique Centers, 
JTRF2020-u2022 does not adopt them. 

The first 695 SINEX files of JTRF2020-u2022 span the updated frame-defining
interval from 2021 (DOY 001, GPS Week 2138) through the end of 2022
(DOY 330, GPS Week 2237). The remaining 1861 SINEX files relate to
the forecast interval from 2022 (DOY 332 GPS Week 2238) through the end
of 2027 (DOY 365, GPS Week 2503) during which SREF stopped assimilating
frame inputs and started operating in forecast mode.

For those of you interested in JTRF2020-u2022, its daily SINEX files
(containing station positions only) can be accessed from the
following URL:

https://sideshow.jpl.nasa.gov/pub/JPL_SREF_Products/JTRF2020_Latest_Updated_Forecasts

Note that the parent directory JTRF2020_Latest_Updated_Forecasts contains
in turn four additional sub-directories named GNSS, VLBI, SLR, DORIS 
each of which hosts 2556 SINEX files characterized by

  (*) GNSS  Stations only in ./JPL_SREF_Products/JTRF2020_Latest_Updated_Forecasts/GNSS
  (*) VLBI  Stations only in ./JPL_SREF_Products/JTRF2020_Latest_Updated_Forecasts/VLBI
  (*) SLR   Stations only in ./JPL_SREF_Products/JTRF2020_Latest_Updated_Forecasts/SLR
  (*) DORIS Stations only in ./JPL_SREF_Products/JTRF2020_Latest_Updated_Forecasts/DORIS

There is a fifth sub-directory ./JPL_SREF_Products/JTRF2020/FULL which
stores 2556 SINEX files with station positions from 931 stations (the full
JTRF2020 network) along with their full covariance (including the
inter-technique covariances).

The daily SINEX files available at

https://sideshow.jpl.nasa.gov/pub/JPL_SREF_Products/JTRF2020_Latest_Updated_Forecasts/

have been grouped in sub-directories categorized by year.
For instance, the sub-directory

https://sideshow.jpl.nasa.gov/pub/JPL_SREF_Products/JTRF2020_Latest_Updated_Forecasts/GNSS/2022

stores the GNSS-only JTRF2020-u2022 SINEX files for the year 2022.

The JTRF2020-u2022 SINEX files under JPL_SREF_Products/JTRF2020_Latest_Updated_Forecasts
are all characterized by unique, non-ambiguous file names adopting the
following convention:

YYYY-MM-DD-noon_jtrf2020_u2022_techID.snx.gz

where

  (*) YYYY   is a 4-digit integer value denoting the Gregorian Year
  (*) MM     is a 2-digit integer value denoting the Month
  (*) DD     is a 2-digit integer value denoting the Day of the Month
  (*) techID is a lowercase string denoting the technique (i.e. gnss, vlbi, slr, doris).

Please, note that for the JTRF2020-u2022 SINEX files under 

./JPL_SREF_Products/JTRF2020_Latest_Updated_Forecasts/FULL

the string _techID is not defined (i.e. YYYY-MM-DD-noon_jtrf2020_u2022.snx.gz).

GNU wget, as well as cURL, can be used to download the JTRF2020-u2022 files.
Here is a couple of examples:

(1) mkdir ./GNSS & wget -b -r -np -P ./GNSS -R "*index.html*" "*.snx" -nH --cut-dirs=4 https://sideshow.jpl.nasa.gov/pub/JPL_SREF_Products/JTRF2020_Latest_Updated_Forecasts/GNSS/2027
(2) mkdir ./GNSS & wget -b -r -np -P ./GNSS -R "*index.html*" "*.snx" -nH --cut-dirs=4 https://sideshow.jpl.nasa.gov/pub/JPL_SREF_Products/JTRF2020_Latest_Updated_Forecasts/GNSS

(1) will download in background mode the GNSS-only JTRF2020-u2022 SINEX files
    for the year 2027 in the directory ./GNSS/2027.
(2) will download in background mode the GNSS-only JTRF2020-u2022 SINEX files
    the whole sub-directory JTRF2020-u2022/GNSS.

The Users are advised that daily EOPs have been removed from the
SINEX files gathered in https://sideshow.jpl.nasa.gov/pub/JPL_SREF_Products/
and will be made available as a separate JTRF2020-u2022 product.

As of this writing, the URL

https://www.jpl.nasa.gov/site/jsgt/jtrf/

is being populated with the entire set of JTRF2020-u2022 products.
We'll be sending out an official email to the community as soon as
the JTRF2020 website gets fully populated with all of the 
JTRF2020-u2022-related files and products.

For those users eager to test time series products out, we made available station 
position time series expressed in the the same ASCII file format consistently adopted
throughout the JTRF website. Such time series can ben found at the following 
URL: 

https://sideshow.jpl.nasa.gov/pub/JPL_SREF_Products/JTRF2020_Additional_Products/jtrf2020-u2022/stations/ 

The structure of the sub-directories under jtrf2020-u2022/stations is 
self-explanatory with the usual distinction in XYZ and ENU time series 
products. It is worth observing that the sub-directories contain time 
series data for all of the 931 stations constituting JTRF. Such time series 
are constructed by "merging" the JTRF2020 with the JTRF2020-u2022 time series 
products.

We wish to acknowledge the crucial contributions provided by the Technique Services
(IVS, ILRS, IGS, IDS) and their tremendous efforts put into the re-analyses
of the space-geodetic databases.

We also would like to thank the ITRS Combination Centres at IGN and
DGFI for their gracious support throughout the JTRF2020-u2022 analyses.

For any comment, question or specific request, please do feel free to contact us.
We will be delighted to accommodate your requests and to help you integrate
JTRF products into your reduction procedures.

We hope you will be able to enjoy JTRF2020-u2022 and we really look forward to having your feedback.

With our warmest regards,

Claudio Abbondanza,
on behalf of the TRF Team at JPL-Caltech

Richard Gross
C Abbondanza
T Chin
M Heflin