NOMAD

 

NOMAD on ExoMars Trace Gas Orbiter 2016

 

Science Orbit Observation Rules

 

 

 

 

 

 

Prepared by : Ian Thomas

tel.: +32 23 73 04 75

email: ian.thomas@aeronomie.be

 

Institute : Belgian Institute for Space Aeronomy

IASB-BIRA

Ringlaan 3 Avenue Circulaire

B-1180 Brussels

Belgium

Document change record

 

version/issue

version/issue date

Paragraphs affected

Reason for change

0/0

27/09/2017

All

Creation of file

0/1

02/10/2017

All

Update following discussion at Ops/UVIS meeting 28/9/17

0/2

05/10/2017

All

Complete update following discussions by email.

0/3

06/10/2017

1

Small corrections

0/4

07/12/2017

2

Corrections to commissioning plan

0/6

28/01/2018

All

Revised commissioning plan

0/7

06/03/2018

All

Added extra observation types, revised commissioning plan to match reality

 

 

 

 

 

 

List of abbreviations

ACS

Atmospheric Chemistry Suite (ExoMars instrument)

AOB

Any Other Business

BIRA

Belgian Institute for Space Aeronomie

CaSSIS

Camera and Stereo Surface Imaging System (ExoMars instrument)

DDS

Data Dissimination Server

EDDS

EGOS Data Dissemination System (data server at ESOC)

EDM

Entry, Descent, Landing Demonstrator Module

ESA

European Space Agency

ESAC

European Space Astronomy Centre

ESOC

European Space Operations Centre

EXM

ExoMars, Exobiology on Mars (ESA & Roscosmos mission)

FREND

Fine Resolution Epithermal Neutron Detector (ExoMars instrument)

FS

Flight Spare Model

HK

Housekeeping

LNO

Limb Nadir and Occultation (NOMAD channel)

MCC

Mid Cruise Checkout

MCO

Mars Capture Orbit

MOR

Mission Operation Report

NEC

Near Earth Commissioning

NOMAD

Nadir and Occultation for Mars Discovery (ExoMars instrument)

OPS

Operations

OU

Open University, England

PFM

Protoflight Model

PSA

Planetary Science Archive

RF

Radio Frequency

S/C

Space-Craft

SMU

Spacecraft Management Unit

SO

Solar Occultation (NOMAD channel)

SWT

Science Working Team

TM

Telemetry

UVIS

Ultraviolet VISible (NOMAD channel)

 

Table of contents

 

1 Introduction.. 5

1.1 Rationale. 5

1.2 Nominal Science Orbit Types. 5

1.2.1 Orbit Type 1: Nominal Science. 6

1.2.2 Orbit Type 2: LNO Cooldown Orbit 6

1.2.3 Orbit Type 3: No NOMAD Occultations. 7

1.2.4 Orbit Type 4: No NOMAD Occultations, LNO Cooldown. 7

1.3 High Beta Angle Science. 8

1.3.1 Orbit Type 5: Grazing / Merged Occultations. 8

1.3.2 Orbit Type 6: Grazing / Merged Occultations, LNO Cooldown. 9

1.4 Special Orbit Types. 10

1.4.1 Orbit Type 7: No NOMAD Occultations, Nightside Nadir 10

1.4.2 Orbit Type 8: LNO Limb. 10

1.5 Calibration Orbit Types. 10

1.5.1 Orbit Type 9: Solar Pointing Calibration. 10

1.6 Other (TBD) Orbit Types. 11

1.6.1 Orbit Type 10: LNO Northern Polar Science (TBD) 11

1.6.2 Orbit Type 11: LNO Southern Polar Science (TBD) 11

1.7 Orbit Template Recap. 12

2 Commissioning Phase. 14

3 Example Observation Plans. 16

3.1 Low Beta Angle (~0-30 degrees) 16

3.2 Medium Beta Angle (~30-60 degrees) 16

3.3 High Beta Angle (~60+ degrees) 16

4 Scheduling Rules. 17

5 Data Volume Considerations. 17

6 Error Checking/Detection of Observations Clashes. 18

6.1 Likely issues. 18

7 Other issues. 18

8 Appendix. 19

8.1 LNO Flip Mirror. 19

8.2 Note Regarding Telecommand Upload Limit 19

8.2.1 Adhering to the current limit 19

8.2.2 Requirements for switching SINBAD on and off 19

 

 


1      Introduction

1.1    Rationale

Planning all observations cannot be done manually; therefore most of the process must be automated using a set of agreed-upon rules. However a single rigid observation plan will not be sufficient, as it will not be able to account for the many variables that NOMAD will experience throughout the science phase. Any plan must:

 

 

As a compromise between automation and flexibility, it is proposed that a set of generic observation templates are to be defined to provide a starting point onto which the detailed planning can be implemented. These orbit templates can be placed into a timeline to generate an initial observation plan, which can then be populated with specific observations.

 

The start/end times of all science observations must be determined from a simple geometric parameter e.g. from occultation eclipse tangent heights, terminator crossing points, or solar zenith angles (SZA).

 

 

 

1.2    Nominal Science Orbit Types

There are several generic observation templates that can be used throughout the mission. These are described below, and will account for the vast majority of all observations. It is currently assumed that SINBAD will remain on throughout and that UVIS is not constrained by any thermal rules. This simplifies the planning considerably; before additional observations were required for UVIS to perform measurements and the northern and southern poles, however these can now be removed from the nominal planning.

Note that here TGO is assumed to be moving from nightside southern hemisphere -> nightside northern hemisphere -> dayside northern hemisphere -> dayside southern hemisphere. For cases where the opposite is true, the observation sequence should be reversed.

If there is a timing conflict between a solar occultation and a nadir pointing block, the solar occultation always takes priority.

The red arrows indicate the TC20 durations.

 


 

1.2.1     Orbit Type 1: Nominal Science

1.2.2     Orbit Type 2: LNO Cooldown Orbit

1.2.3     Orbit Type 3: No NOMAD Occultations

1.2.4     Orbit Type 4: No NOMAD Occultations, LNO Cooldown

1.3    High Beta Angle Science

For certain measurements at high beta angles, ingress and egress occultations may need to be merged, or the tangent altitude may not reach the surface. At other times, the nominal science orbit types above will be used.

1.3.1     Orbit Type 5: Grazing / Merged Occultations

1.3.2     Orbit Type 6: Grazing / Merged Occultations, LNO Cooldown

 

1.4    Special Orbit Types

These will be used occasionally to achieve specific science objectives. These should not be considered a part of the nominal science plan.

 

1.4.1     Orbit Type 7: No NOMAD Occultations, Day + Nightside Nadirs

1.4.2     Orbit Type 17: No NOMAD Occultations, UVIS Day + Nightside Nadir, LNO Dayside Nadir only

1.4.3     Orbit Type 27: No NOMAD Occultations, UVIS Day + Nightside Nadir, LNO Nightside Limb + Dayside Nadir

1.4.4     Orbit Type 37: No NOMAD Occultations, LNO + UVIS Nightside Nadir, UVIS Dayside Nadir

 

1.4.5     Orbit Type 8: LNO Dayside Limb, UVIS Nadir, with Solar Occultations

This observation is dependent on the position of the Sun and so may need to be determined manually by the science team for specific orbits. 2x telecommands are required to move the LNO flip mirror to/from the solar position.

 

 

1.4.6     Orbit Type 18: LNO Limb, UVIS nadir, no NOMAD Occultations

 

 

 

1.4.7     Orbit Type 28: True LNO + UVIS nadir with TGO rotation to limb (TBD)

This is currently forbidden by the spacecraft pointing rules, but could be useful in future planning cycles if allowed.

 

 

 

 

1.5    Calibration Orbit Types

1.5.1     Orbit Type 9: Solar Pointing Calibration

These will be scheduled during the no-eclipse seasons at high beta angle. Solar pointing blocks are required to perform the majority of these measurements and hence cannot be planned until more is known about the spacecraft limitations. Solar pointing blocks of ~60 minutes each would be the preferred method of running these calibrations.

 

1.6    Other (TBD) Orbit Types

1.6.1     Orbit Type 10: LNO Northern Polar Science (TBD)

1.6.2     Orbit Type 11: LNO Southern Polar Science (TBD)


 

1.6.3     Orbit Type 12/OFF: NOMAD Off

 

1.7    Orbit Template Recap

         OT1: Nominal science

o    2x SO+UVIS solar occultations

o    LNO mid-latitude dayside nadir

o    UVIS full dayside nadir

o    LNO cooldown periods on nightside and around north and south poles

 

         OT2: LNO cooldown

o    2x SO+UVIS solar occultations

o    UVIS full dayside nadir

o    LNO cooldown periods on nightside, complete dayside, and around north and south poles

 

         OT3: No occultations

o    LNO+UVIS full dayside nadir

o    LNO cooldown periods on complete nightside

 

         OT4: No occultations, LNO cooldown

o    UVIS northern polar nadir

o    UVIS dayside nadir

o    UVIS southern polar nadir

 

         OT5: Long occultation

o    1x SO+UVIS solar occultation

o    LNO mid-latitude dayside nadir

o    UVIS full dayside nadir

o    LNO cooldown periods around north and south poles

 

         OT6: Long occultation, LNO cooldown

o    1x SO+UVIS solar occultation

o    UVIS full dayside nadir

o    LNO cooldown periods on complete dayside and around north and south poles

 

         OT7: Day and Nightside nadirs

o    LNO+UVIS mid-latitude nightside nadir

o    LNO mid-latitude dayside nadir

o    UVIS full dayside nadir

o    LNO cooldown periods around north and south poles

 

         OT17: UVIS day and nightside nadir, LNO dayside nadir only

o    UVIS mid-latitude nightside nadir

o    LNO mid-latitude dayside nadir

o    UVIS full dayside nadir

 

         OT27: UVIS day and nightside nadir, LNO dayside nadir and nightside limb

o    LNO mid-latitude nightside limb

o    UVIS mid-latitude nightside nadir

o    LNO mid-latitude dayside nadir

o    UVIS full dayside nadir

o    LNO cooldown periods around north and south poles

 

         OT37: UVIS day and nightside nadir, LNO nightside nadir only

o    LNO+UVIS mid-latitude nightside nadir

o    UVIS full dayside nadir

 

         OT47: UVIS day and nightside nadir, LNO nightside limb only

o    LNO mid-latitude nightside limb

o    UVIS mid-latitude nightside nadir

o    UVIS full dayside nadir

 

         OT8: LNO dayside limb with occulations

o    2x SO+UVIS solar occultations

o    LNO mid-latitude dayside limb

o    UVIS full dayside nadir

o    LNO cooldown periods around north and south poles

 

         OT18: LNO dayside limb, no occultations

o    LNO full dayside limb

o    UVIS full dayside nadir

o    LNO cooldown periods on nightside and around north and south poles

 

         OT28: LNO+UVIS true dayside limb, no occultations (TBD)

o    LNO+UVIS full dayside limb

o    LNO cooldown periods on nightside

 

         OT9: Solar calibration

o    SO/LNO/UVIS solar pointing blocks

 

         OT10: LNO northern pole (TBD if required)

o    2x SO+UVIS solar occultations

o    LNO north pole and mid-latitude dayside nadir

o    UVIS full dayside nadir

o    LNO cooldown periods on nightside and around dayside southern latitudes

 

         OT11: LNO southern pole (TBD if required)

o    2x SO+UVIS solar occultations

o    LNO mid-latitude dayside and south pole nadir

o    UVIS full dayside nadir

o    LNO cooldown periods on nightside and around dayside northern latitudes

 

         OT12/OFF: NOMAD off: no occultations, no nadirs

o    Full cooldown orbit

 

 

 


 

2      Commissioning Phase

Before the nominal science mission begins, there will be a commissioning phase lasting 4-6 weeks in which TGO will operate in nadir mode only (no dedicated pointings).

This period presents an ideal time to determine the thermal constraints of NOMAD by running various configurations that could be used throughout the mission. To make the tests accurate, the SO channel will be run for the solar occultations, though the data will not be usable as the channel will not be pointed to the sun. Several configurations will be tested:

 

NOMAD thermal baseline orbits:

 

Day 1: SINBAD-UVIS observation thermal baseline.

OT:

4

4

4

4

4

4

4

4

4

4

4

3

 

SO-LNO cooldown test orbits:

 

Day 2: 2 orbits of nominal science, observing the 80:40 rule. SINBAD remains on throughout. UVIS dayside nadirs.

OT:

4

4

4

4

4

3

4

4

4

4

4

3

 

 

 

 

 

 

 

 

80:40 rule with 1/2 LNO cooldown orbits:

 

Day 3: 6 orbits of nominal science, observing the 80:40 rule with regular LNO cooldown orbits. SINBAD remains on throughout. UVIS dayside nadirs.

OT:

4

3

4

3

4

3

4

3

4

3

4

3

 

Day 4: 6 orbits of thermal baseline cooldown.

OT:

4

4

4

4

4

4

 

80:40 rule with 1/3 LNO cooldown orbits:

 

Day 4.5: 8 orbits of nominal science, observing a 80:40 rule with regular LNO cooldown orbits. SINBAD remains on throughout. UVIS dayside nadirs.

OT:

4

3

3

4

3

3

4

3

3

4

3

3

 

Day 5.5: 6 orbits of thermal baseline cooldown.

OT:

4

4

4

4

4

4

 

80:40 rule with no LNO cooldown orbits:

 

Day 6: 12 orbits of nominal science, observing a 80:40 rule. SINBAD remains on throughout. UVIS dayside nadirs.

OT:

3

3

3

3

3

3

3

3

3

3

3

3

 

Day 7: 6 orbits of thermal baseline cooldown.

OT:

4

4

4

4

4

4

 

 

60:60 rule with 1/2 LNO cooldown orbits:

 

Day 7.5: 6 orbits of nominal science, observing the 60:60 rule with regular LNO cooldown orbits. SINBAD remains on throughout. UVIS dayside nadirs.

OT:

4

3

4

3

4

3

4

3

4

3

4

3

 

Day 8.5: 6 orbits of thermal baseline cooldown.

OT:

4

4

4

4

4

4

 

60:60 rule with 1/3 LNO cooldown orbits:

 

Day 9: 8 orbits of nominal science, observing a 60:60 rule with regular LNO cooldown orbits. SINBAD remains on throughout. UVIS dayside nadirs.

OT:

4

3

3

4

3

3

4

3

3

4

3

3

 

Day 10: 6 orbits of thermal baseline cooldown.

OT:

4

4

4

4

4

4

 

60:60 rule with no LNO cooldown orbits:

 

Day 10.5: 12 orbits of nominal science, observing a 60:60 rule. SINBAD remains on throughout. UVIS dayside nadirs.

OT:

3

3

3

3

3

3

3

3

3

3

3

3

 

Day 11.5: 6 orbits of thermal baseline cooldown.

OT:

4

4

4

4

4

4

 

 

 

 

80:40 rule with 1/2 LNO cooldown orbits SINBAD off:

 

Day 12: 6 orbits of nominal science, observing the 80:40 rule with regular LNO cooldown orbits. SINBAD off for non-operational orbits. UVIS dayside nadirs.

OT:

OFF

3

OFF

3

OFF

3

OFF

3

OFF

3

OFF

3

 

Day 13: 6 orbits of thermal baseline cooldown.

OT:

4

4

4

4

4

4

 

80:40 rule with 1/3 LNO cooldown orbits SINBAD off:

 

Day 13.5: 8 orbits of nominal science, observing a 80:40 rule with regular LNO cooldown orbits. SINBAD off for non-operational orbits. UVIS dayside nadirs.

OT:

OFF

3

3

OFF

3

3

OFF

3

3

OFF

3

3

 

Day 14.5: 6 orbits of thermal baseline cooldown.

OT:

4

4

4

4

4

4

 

80:40 rule with no LNO cooldown orbits SINBAD off:

 

Day 15: 12 orbits of nominal science, observing a 80:40 rule. SINBAD off when not observing. UVIS dayside nadirs.

OT:

3

3

3

3

3

3

3

3

3

3

3

3

 

Day 16: 6 orbits of thermal baseline cooldown.

OT:

4

4

4

4

4

4

60:60 rule with 1/2 LNO cooldown orbits SINBAD off:

 

Day 16.5: 6 orbits of nominal science, observing the 60:60 rule with regular LNO cooldown orbits. SINBAD off for non-operational orbits. UVIS dayside nadirs.

OT:

OFF

3

OFF

3

OFF

3

OFF

3

OFF

3

OFF

3

 

Day 17.5: 6 orbits of thermal baseline cooldown.

OT:

4

4

4

4

4

4

 

60:60 rule with 1/3 LNO cooldown orbits SINBAD off:

 

Day 18: 8 orbits of nominal science, observing a 60:60 rule with regular LNO cooldown orbits. SINBAD off for non-operational orbits. UVIS dayside nadirs.

OT:

OFF

3

3

OFF

3

3

OFF

3

3

OFF

3

3

 

Day 19: 6 orbits of thermal baseline cooldown.

OT:

4

4

4

4

4

4

 

60:60 rule with no LNO cooldown orbits SINBAD off:

 

Day 19.5: 12 orbits of nominal science, observing a 60:60 rule. SINBAD off when not observing. UVIS dayside nadirs.

OT:

3

3

3

3

3

3

3

3

3

3

3

3

 

Day 20.5: 6 orbits of thermal baseline cooldown.

OT:

4

4

4

4

4

4

 

 

 

 

Test measurements:

 

Day 21: 6 orbits of nightside nadirs, observing a 80:40 rule with regular LNO cooldown orbits. 6 orbits of limb measurements, observing a 80:40 rule with regular LNO cooldown orbits. SINBAD remains on throughout.

OT:

37

37

4

37

37

4

8

8

4

8

8

4

 

Day 22: 6 orbits of thermal baseline cooldown.

OT:

4

4

4

4

4

4

 

 

 

Measurement sequence repeats until end of commissioning phase:

 

Extra tests and calibrations could be foreseen during this phase, provided that they comply with the requirement that TGO is always nadir pointed. For example, dark calibrations could be performed on the nightside, or additional thermal tests (running channels for long periods) would be possible. For now, nothing extra is foreseen and therefore the remainder of the commissioning phase is filled by repeating the start of the observation sequence i.e.

 

 

 

 

80:40 rule with 1/2 LNO cooldown orbits (repeated from above):

 

Day 22.5: 6 orbits of nominal science, observing the 80:40 rule with regular LNO cooldown orbits. SINBAD remains on throughout. UVIS dayside nadirs.

OT:

4

3

4

3

4

3

4

3

4

3

4

3

 

Day 23.5: 6 orbits of thermal baseline cooldown.

OT:

4

4

4

4

4

4

 

80:40 rule with 1/3 LNO cooldown orbits (repeated from above):

 

Day 24: 8 orbits of nominal science, observing a 80:40 rule with regular LNO cooldown orbits. SINBAD remains on throughout. UVIS dayside nadirs.

OT:

4

3

3

4

3

3

4

3

3

4

3

3

 

Day 25: 6 orbits of thermal baseline cooldown.

OT:

4

4

4

4

4

4

 

80:40 rule with no LNO cooldown orbits (repeated from above):

 

Day 25.5: 12 orbits of nominal science, observing a 80:40 rule. SINBAD remains on throughout. UVIS dayside nadirs.

OT:

3

3

3

3

3

3

3

3

3

3

3

3

 

Day 26.5: 6 orbits of thermal baseline cooldown.

OT:

4

4

4

4

4

4

 

60:60 rule with 1/2 LNO cooldown orbits(repeated from above):

 

Day 27: 6 orbits of nominal science, observing the 60:60 rule with regular LNO cooldown orbits. SINBAD remains on throughout. UVIS dayside nadirs.

OT:

4

3

4

3

4

3

4

3

4

3

4

3

 

Day 28: 6 orbits of thermal baseline cooldown.

OT:

4

4

4

4

4

4

 

60:60 rule with 1/3 LNO cooldown orbits:

 

Day 28.5: 5 orbits of nominal science, observing a 60:60 rule with regular LNO cooldown orbits. SINBAD remains on throughout. UVIS dayside nadirs.

OT:

4

3

3

4

3

3

4

3

END OF MTP

 

 


 

3      Example Observation Plans

Observation plans will be determined by the science team, comprising of a sequential list of orbit types. Several potential observation plans are given below.

 

3.1    Low Beta Angle (~0-30 degrees)

This regime accounts for approximately 50% of all orbits. Here the two occultations are ~20-30 minutes apart and the SZA is small on the dayside.

 

NOMAD will be allocated solar occultations on 2/3 of the orbits, therefore a measurement schedule could be as follows. The 80:40 rule can be applied until the commissioning phase results are analysed:

OT:

1

1

4

1

1

4

1

1

4

1

1

4

 

3.2    Medium Beta Angle (~30-60 degrees)

Here the two occultations are closer together and the SZA has higher values on the dayside. No nightside nadirs will be performed between the two solar occultations. MBA1 or 2 polar measurement templates may need to be suspended due to SO channel precooling, hence there may be a reduction in measurements of either pole.

 

The SO channel requires 10 minutes of precooling before each occultation measurement, therefore if the duration between the occultations is smaller than this then the observations will be merged.

Observations can be split into five orbit templates:

 

NOMAD will be allocated solar occultations on 2/3 of the orbits, therefore a measurement schedule could be as follows. The 80:40 rule can be applied until the commissioning phase results are analysed:

OT:

1

1

4

1

1

4

1

1

4

1

1

4

 

If the occultations are merged then the following would be preferable:

OT:

5

5

4

5

5

4

5

5

4

5

5

4

 

3.3    High Beta Angle (~60+ degrees)

Here the occultation tangent height never reaches 0km and TGO is always illuminated by the Sun. Atmospheric measurements can be made if the tangent height drops below TBD km, otherwise solar calibration measurements e.g. miniscans and fullscans should be run instead. The SZA is very high for nadir observations, reducing SNR of dayside nadir measurements, therefore the flip mirror could be used to perform LNO limb measurements if the solar geometry is suitable.

 

NOMAD will be allocated solar occultations on 2/3 of the orbits, therefore a measurement schedule could be as follows. The 80:40 rule can be applied until the commissioning phase results are analysed:

OT:

1

1

4

1

1

4

1

1

4

1

1

4

 

If the occultations are merged then the following would be preferable:

OT:

5

5

4

5

5

4

5

5

4

5

5

4

 

If the tangent height is high, nadir-only measurements could be made instead:

OT:

3

3

4

3

3

4

3

3

4

3

3

4

 

Or calibration measurements could be considered, depending on the length of time since the previous calibration campaign:

OT:

9

9

9

9

9

9

9

9

9

9

9

9

 

Calibration or limb measurements will likely be scheduled manually: the science team will provide a list of calibration observations, including a complete TC20 and a pointing type (e.g. solar pointing SO boresight), once an estimate of the time available has been estimated. If all measurements cannot be made in the allocated time the science team will be informed and a reduced list will be provided (and likewise if there is time available for additional measurements).

 

 

 

 

4      Scheduling Rules

 

5      Data Volume Considerations

 

 

6      Error Checking/Detection of Observations Clashes

6.1    Likely issues

         Clashes between solar occultation precooling and nadir polar observations

         Incorporating targeted observations e.g. Mars rovers into the planning

         Planning of other instruments e.g. CaSSIS off-nadir pointing requests

         TGO manoeuvres are not yet accounted for in the planning. Regular stoppages will be required but are currently unknown. It is unclear how solar calibrations will be scheduled when beta angle is high

         TGO and other instrument illumination constraints e.g. CaSSIS pointing vs. solar illumination angle

 

7      Other issues

Turn-around time from commissioning phase to implementation of on/off timing rule. Baseline is 80 minutes on: 40 minutes off, but this may result in the LNO channel running hot.

 

 

8      Appendix

8.1    LNO Flip Mirror

Each flip mirror change requires a single TC70. LNO will not be used for solar occultations, and therefore the flip mirror can remain in nadir position throughout. It should be moved only before and after a limb measurement or before/after a calibration campaign.

 

 

8.2    Note Regarding Telecommand Upload Limit

8.2.1     Adhering to the current limit

Note that this assumes unlimited TCs. If this is not the case then the plan will need to be modified to reduce the number of observations. In particular, if the current limit (750 TCs per 5 day period) is to be kept then switching SINBAD off for regular cool-down periods will never be possible.

 

Each measurement requires 3 TCs:

         Open PDHU

         Send TC20

         Close PDHU

 

Therefore 750 TCs per 5 days = 150 TCs per day = 12 TCs per orbit = 4 observations per orbit, not including LNO flip mirror manipulations.

 

 

8.2.2     Requirements for switching SINBAD on and off

 

The SINBAD switch on sequence requires 10 TCs, including the opening of the PDHU file

The SINBAD switch off sequence requires 12 TCs, including the closing of the PDHU file

 

Therefore to switch on+off fully once per orbit requires ~20 TCs per orbit = 240 TCs per day = 1200 TCs per 5 day period. The limit would need to be tripled to make this feasible.