ILRS Missions Working Group Meeting
Of the International Laser Ranging Service
(ILRS)
Nice, France
April 23, 2002
Attendees:
Graham Appleby, David Carter, John Degnan, Bud Donovan, Werner
Gurtner, Julie Horvath, Van Husson, Jim Long, Carey Noll, Ron
Noomen, Toshi Otsubo, Mike Pearlman, Ivan Prochazka, Randy
Ricklefs, Ulli Schreiber, Wolfgang Schluter, Wolfgang Seemueller,
Peter Shelus, Scott Wetzel
Topics Discussed:
MWG membership and Review of Efforts since Last Meeting
Campaign Status
Recent Launches and New Missions
Upcoming Missions
Other Mission News
Other Issues
Satellite Tracking Priority List
MWG Membership and Review of Efforts since Last Meeting
There was a general discussion on the need for new members was
made. Also, the following topics were discussed as to what
MWG actions were either completed or initiated since the last
meeting. Included was the need for a change in the Mission Support
Request Form to reflect the satellite name in the mail message
Subject line. Also, the new mailing list which includes the
coordinators for each of the working groups (AWG, NW&E,
DF&P, and the TIGER teams), the director of the CB, the
secretary of the CB and the Chairman of GB has gone into operation
and has worked well on MWG issues.
Campaign Status
Etalon-1, -2
Ron Noomen provided a report on the success of the Etalon
tracking campaign. The Analysis Working Group (AWG)
originally requested this campaign in Nice, France, in March
2001. This 6-month campaign was requested to determine if a
robust data set from Etalon 1 & 2 would improve Earth
Orientation Parameters (EOP) in the SLR solutions. The
campaign was extended at the Toulouse meeting until the end of
March ‘02 and was further extended by the Governing Board
until the Nice meeting for convenience.
Results provided by Noomen showed that despite data volume
increased by a factor of 2, EOP improvement was small
(~5%). Noomen stated that the campaign should continue
despite of the small improvement in EOP as the data could support
other aspects of the program, namely station bias, GM and gravity
field study. The AWG was tasked to meet the next week and
develop a requirement for requesting the extension for the Etalon
campaign.
LRE (Laser Ranging Equipment)
Maki Maeda from NASDA provided a report on the LRE
campaign. The Official LRE campaign was to last 1 month in
September 2001. Due to a 3 hour delay in launch it became
very difficult to acquire the target as LRE lost good terminator
conditions for the first 3 months of the overall mission.
Grasse LLR station finally caught it in December 2001, then
Yarragadee, then CRL.
NASDA would like to keep the LRE campaign going on a
“track as you can” basis and will provide TIRV’s
routinely and keep LRE at the bottom of the tracking priority
list. Lessons Learned from the campaign includes that the
ILRS was not ready for this type of campaign, we need to work on
better station pointing. Wetzel also requested that the LRE
team provide retroreflector specifications to confirm the
compensation basis for the velocity abberation. Toshi Otsubo
stated that he had given a paper in the Toulouse meeting in 2001
and would forward a copy of the paper to the MWG.
Reflector
Reflector is a Russian satellite launched on December 10, 2001,
where SLR is used to support POD research for space debris
detection . Temporary emergency approval was given by
the GB on December 20, 2001 to support a campaign with a duration
of 9 months. SLR began on December 21, 2001. The first
operational Reflector pass received by Yarragadee. Since
then, tracking leaders are Yarragadee, Monument Peak and Graz with
a total of 28 systems currently tracking Reflector. The
success of campaign needs to be reviewed by IPIE and a report needs
to be filed by the IPIE to the MWG and ILRS.
Starshine 3
Starshine 3 was never determined to be an ILRS supported
satellite. The Starshine satellites were to be tracked by
NASA stations and others if desired to determine utility of the
retroreflectors.
Starshine 3 launched on September 30, 2001. The
firstStarshine-3 pass received by Yarragadee on October 3,
2001. Since Starshine-3 was not an ILRS supported mission,
tracking limited to NASA stations and anyone who wanted to try
tracking. There were a total of 9 systems tracking Starshine
3.
In an effort to increase the quality of the predictions, NRL
provided high quality predictions to help support
acquisition. Although this has aided in acquisition, the low
altitude and lack of tracking has made it difficult to acquire
Starshine 3. Starshine-3 scheduled to de-orbit on
approximately October 30, 2002
Starshine 2
Starshine 2 was deployed from STS-108 on December 16,
2001. No tracking attempted due to limitations of tracking
Starshine 3. Currently, Starshine is predicted to decay
Apr 26, 2235Z
Recent Launches and New Missions
Jason
Jason was launched on Dec. 7, 2001 and placed in tandem orbit
with TOPEX/ Poseidon (~1 minute separation, Jason leading).
SLR was attempted by several systems prior to operational
commitment to confirm array performance. SLR tracking of
Jason officially began on January 14, 2002 with the first
operational Jason pass received by Yarragadee. Since then,
tracking leaders are Yarragadee, Graz with good support from
Monument Peak, Greenbelt, Zimmerwald & Wettzell. There
are currently 32 systems tracking Jason.
Tracking scenario as requested from Jason Team has been
discussed with the MWG since prior to the launch of Jason with
tracking to occur by alternating successful full-pass tracking
between Jason and TOPEX/Poseidon. Systems can pick up first
minute of Jason pass when tracking TOPEX or last minute of TOPEX
when tracking Jason. Currently, several systems are
experimenting with interleaving during each pass - being reviewed
by Jason team. The Jason team is examining these passes and
will continue to work with the MWG on a formal tracking
procedure.
Envisat-1
Envisat-1 launched on March 1, 2002 and placed in tandem orbit
with ERS-2 (~30 minute separation)
SLR scheduled to begin at ~launch + 40 days, began on April 10,
2002. The first Envisat pass received by Metsahovi and Riga
(same time). Since then, tracking leaders are Metsahovi,
Monument Peak and Herstmonceux. Currently 11 systems tracking
Envisat-1. A member of the Envisat-1 team was to provide
status at ILRS General Assembly
GRACE
GRACE A&B were launched on March 17, 2002 and placed in
tandem orbit with each other (~30 secs separation). SLR was
required ASAP from separation from S/C. A tracking scenario
as requested from GRACE Team which included alternating successful
full-pass tracking between GRACE A & B unless systems are able
to quickly alternate between satellites. Currently, several
systems are experimenting with interleaving during each pass.
The data is being reviewed by GRACE team.
The first GRACE A pass received by Yarragadee. Tracking
leaders in the beginning of the mission are Yarragadee,
Herstmonceux. The first GRACE B pass received by
Yarragadee. Tracking leaders in the beginning of the mission
are Yarragadee, Herstmonceux, and Monument Peak
Currently there almost twice as many GRACE A passes as GRACE
B. What is the impact on GRACE and why is this happening are
the current questions to be resolved. The GRACE team is to
provide status at ILRS General Assembly
Meteor-3M
Meteor-3M was launched on December 10, 2001 along with
Reflector. Meteor-3M is using an Optical Luneberg Lens for
SLR tracking that was shown at several SLR meetings in the
past. SLR was originally limited by agreement to Greenbelt,
Monument Peak and a Russian station near Moscow as a test
only. The SAGE project, a NASA instrument on board Meteor-3M
was concerned about interference in their solar experiments,
consequently there were several restrictions in tracking like,
limited stations, restricted tracking elevations and tracking in
nighttime hours only.
At a meeting with the SAGE team in February it was disclosed
that the GLONASS/GPS receiver on-board Meteor-3M was not
function.. SLR had now become the only method for POD in
support of SAGE. Until then Meteor-3M was supported by radar
tracking which was to end on April 30, 2002. The SAGE team
requested to Meteor-3M group to support SLR with no restrictions
for elevation or daylight tracking and would include tracking by
the entire ILRS network.
On April 3rd a Mission Support Request Form was submitted for
ILRS support of Meteor-3M. Based on limited responses MWG
endorsed support for Meteor-3M.
The ILRS GB approved support at GB meeting on April
24th with tracking to begin ASAP.
Upcoming Missions
Wetzel presented the updated table that included the upcoming
ILRS missions for the next few years. They are shown in the
table below. This table has been updated to include the
Starshine 4/5 mission.
Upcoming Missions
Satellite
|
Owner
|
Mission Type
|
Planned Launch Date
|
Mission Duration
|
Received Mission Request Form
|
Received ILRS GB Approval
|
Meteor-3M
|
ROSAVIACOSMOS
|
Solar Research / new array testing
|
Dec 10, 2001
|
3 years
|
Yes
|
Yes
|
IceSat (GLAS)
|
NASA
|
Ice sheet research
|
Dec 16, 2002
|
3-5 years
|
Yes
|
Yes
|
Gravity Probe B
|
NASA
|
Relativity research
|
Oct 30, 2002
|
1-2 years
|
Yes
|
Yes
|
ADEOS-II
|
NASDA
|
Altimeter calibration
|
Nov 2002
|
3 years
|
Yes
|
Yes
|
Starshine 4/5
|
Starshine
|
Atmosphere Density
|
Jan 2003
|
6 months
|
No
|
No
|
CryoSat
|
ESA
|
Earth Sensing
|
Apr/May 2004
|
3.5 years
|
Yes
|
Awaiting MWG Recommendation
|
ALOS
|
NASDA
|
Altimeter calibration
|
Jul/Aug. 2004
|
3 years
|
No
|
No
|
ETS-VIII
|
NASDA
|
Time transfer experiment
|
Jul./Aug. 2004
|
3 years
|
No
|
No
|
ADEOS-II (Advanced Earth Observing Satellite)
Takashi Uchimura from NASDA provided a report on the ADEOS-II
satellite and the SLR support requirements. ADEOS-II is an
Earth Sensing mission hosted by NASDA that is currently scheduled
to be launched between November 1-30, 2002. SLR support is
currently to occur for only the first 39 days of the mission
to support POD. During this time the GPS receiver will be
turned off.
NASDA believes that the on-board Global Imager (GLI) is
sensitive to the 532 nm lasr and my be damaged if explosed to laser
radiation from the ILRS. Based on NASDA’s concerns,
Uchimura provided 2 options for support for dates past Launch + 39
days (L+39). They include:
Full SLR support for only the first 39 days of the mission
Full SLR support for the first 39 days of the mission, then
restrict SLR tracking of ADEOS-II to the areas provided by NASDA in
a tracking mask in order to eliminate illumination of GLI in
restricted area of sensor
It was generally agreed upon that option 2 would not be
realistic since no system could not guarantee not tracking in the
restricted area without extensive hardware/software/procedure
modifications.
Action Item:
Uchimura will provide specifications for the GLI to MWG for
analysis for possible GLI damage from SLR.
ICESat (Ice, Cloud, and Land Elevation Satellite)
Peter Shelus, UTEX/CSR, presented a review for the ICESat
satellite mission and the SLR requirements. ICESat is a NASA
mission to measure the ice sheet mass, balance, cloud and aerosol
heights, optical densities, vegetation and land topography hosted
by NASA / CSR. ICESat is currently scheduled to be launched
in December 16, 2002. Preparations for SLR support are
ongoing at University of Texas, with good coordination with
ILRS. Currently, HTSI to include GPS data in prediction
generation.
The current tracking scenario will include:
array confirmation only for L+30 days, then,
tracking at high priority until L+6 months, then
Place ICESat in standard ILRS tracking priority.
GPB (Gravity Probe B)
Scott Wetzel provided a brief report on the Gravity Probe-B
mission. GPB is a NASA / Stanford University relativity
mission which is scheduled for launch in October 2002.
Coordination between NASA, HTSI, and Stanford University is ongoing
with the mission support document being developed and is currently
in review.
Starshine 4/5
Scott Wetzel provided a brief report on the upcoming Starshine
4/5 mission. NASA has firmly manifested Starshine 4/5
dual-satellite experiment on the STS-114 Shuttle mission to the
International Space Station in January of 2003.
Starshine 4/5 will have mounted 1000 mirrors and 31 laser
retroreflectors on its external shell.
The Starshine 4/5 Mission Plan includes, the release from
Starshine 4, a 4 inch (10 cm) hollow aluminum sphere, instead,
which will be Starshine 5. This small sub-satellite
will be released shortly after Starshine 4 is deployed from Space
Shuttle Atlantis. Both Starshine 4 and 5 will carry 31 laser
retroreflectors on their surfaces, and Starshine 5 will have no
mirrors and will thus not be naked-eye visible, so tracking will
dependent totally on ILRS (if approved) and Space Command tracking
for orbit determination.
By comparing the orbital decay rates of Starshine 4 and 5, it
will possible for to determine the density of the earth's
atmosphere more precisely than we've been able to do on previous
missions.
Other Mission News
Mission Status Changes
Wetzel reported the following changes in mission status that
occurred during the previous period.
BEC had its mission status change from a campaign to full
mission status in January 2002, see SLR Mail No. 0873 on January 3,
2002. The UTex/CSR requested Mission Status to strengthen
long-term changes in gravity field. BEC retains same tracking
priority level as during campaign.
SLR support for WESTPAC was suspended in January 2002, see SLR
Mail No. 0877 on January 7, 2002. WESTPAC was being used for very
little for research and the data set was very weak and the
satellite was difficult to acquire satellite. The satellite
originators agreed with the suspension of SLR support.
At the request of the IGLOS-PP, the set of 3 GLONASS satellites
to be tracked by SLR was changed to 84, 86 and 87, see SLR Mail No.
0900 on February 20, 2002. All GLONASS satellites supported
now all have the same type of (reduced sized) retroreflector
arrays. The new array time limits some stations to
night time tracking only resulting in loss of data
Missions to drop from list
Wetzel reported that the following upcoming missions were to be
dropped from the tracking list of new satellites and provided a
brief explanation for why they were dropped. Included were
the OICETS from NASDA and VCL from NASA whose missions are
indefinitely postponed. No response from the IRS-P5 from
ISRO, and SAC-C from CONAE for a long period of time are the reason
for dropping these missions from the list.
Other Issues
Dynamic Tracking Priorities
Peter Shelus recommended that we continuously monitor all
tracking and adjust tracking priorities to pick up on weak
satellites. Scott Wetzel took the action item to work this issue
from the MWG.
Weak initial tracking support of new satellites
Scott Wetzel reported early analysis about weak tracking support
on new satellites. For the first several weeks of tracking of
new satellites usually have same few stations supporting with
others following later. This should not be happening during
critical phase of mission. Possible causes are being
investigated at HTSI.
More information about Mission Support planning and
implementation status on web
Greater detail to the mission summaries with respect to mission
support activities will be posted on the web
Spacecraft COM. The MWG responsible for providing
Signal Processing Group S/C COM models from satellite host.
This needs to be done in the early stages of mission planning.
Next Meeting
The next ILRS Missions Working Group Meeting will occur at the
13th International Laser Ranging Instrumentation
Workshop in Washington DC, USA during the week of October 7-11,
2002.
Current Tracking Priorities
Responsible Government Official:
NASA's
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